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	$35.50	4.845%	$37.22	$37.22	$37.20	$37.20
Purchase #2	$127.95	4.251%	$133.3892	$133.39	$133.40	$133.40
Purchase #3	$199.86	7.820%	$215.4891	$215.49	$215.50	$215.50
Purchase #4	$178.44	5.688%	$188.5897	$188.59	$188.60	$188.60
Purchase #5	$157.73	7.240%	$169.1497	$169.15	$169.15	$169.10
Purchase #6	$168.30	6.335%	$178.9618	$178.96	$178.95	$179.00
Purchase #7	$156.79	7.245%	$168.1494	$168.15	$168.15	$168.10
7 purchase totals =	$1,024.57		$1,090.9489	$1,090.95	$1,090.95	$1,090.90