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	$219.65	6.721%	$234.4127	$234.41	$234.40	$234.40
Purchase #2	$132.26	7.450%	$142.1134	$142.11	$142.10	$142.10
Purchase #3	$73.86	13.527%	$83.851	$83.85	$83.85	$83.90
Purchase #4	$51.93	3.690%	$53.8462	$53.85	$53.85	$53.80
Purchase #5	$226.46	7.700%	$243.8974	$243.90	$243.90	$243.90
Purchase #6	$74.65	12.130%	$83.705	$83.71	$83.70	$83.70
Purchase #7	$241.36	4.179%	$251.4464	$251.45	$251.45	$251.40
7 purchase totals =	$1,020.17		$1,093.2721	$1,093.28	$1,093.25	$1,093.20