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	$149.57	7.250%	$160.4138	$160.41	$160.40	$160.40
Purchase #2	$136.33	12.457%	$153.3126	$153.31	$153.30	$153.30
Purchase #3	$119.46	3.351%	$123.4631	$123.46	$123.45	$123.50
Purchase #4	$107.83	3.590%	$111.7011	$111.70	$111.70	$111.70
Purchase #5	$36.72	11.445%	$40.9226	$40.92	$40.90	$40.90
Purchase #6	$154.93	5.383%	$163.2699	$163.27	$163.25	$163.30
Purchase #7	$153.81	5.261%	$161.9019	$161.90	$161.90	$161.90
7 purchase totals =	$858.65		$914.9850	$914.97	$914.90	$915.00