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	$151.71	13.445%	$172.1074	$172.11	$172.10	$172.10
Purchase #2	$227.77	11.554%	$254.0865	$254.09	$254.10	$254.10
Purchase #3	$120.88	3.829%	$125.5085	$125.51	$125.50	$125.50
Purchase #4	$217.81	10.618%	$240.9371	$240.94	$240.95	$240.90
Purchase #5	$150.75	12.290%	$169.2772	$169.28	$169.30	$169.30
Purchase #6	$107.77	3.708%	$111.7661	$111.77	$111.75	$111.80
Purchase #7	$18.53	5.577%	$19.5634	$19.56	$19.55	$19.60
7 purchase totals =	$995.22		$1,093.2462	$1,093.26	$1,093.25	$1,093.30