Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$188.71	4.212%	$196.6585	$196.66	$196.65	$196.70
Purchase #2	$111.88	13.563%	$127.0543	$127.05	$127.05	$127.10
Purchase #3	$174.32	9.871%	$191.5271	$191.53	$191.55	$191.50
Purchase #4	$250.90	11.513%	$279.7861	$279.79	$279.80	$279.80
Purchase #5	$141.45	13.115%	$160.0012	$160.00	$160.00	$160.00
Purchase #6	$159.32	11.128%	$177.0491	$177.05	$177.05	$177.00
Purchase #7	$162.69	4.451%	$169.9313	$169.93	$169.95	$169.90
7 purchase totals =	$1,189.27		$1,302.0076	$1,302.01	$1,302.05	$1,302.00