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	$57.68	4.813%	$60.4561	$60.46	$60.45	$60.50
Purchase #2	$204.98	11.516%	$228.5855	$228.59	$228.60	$228.60
Purchase #3	$185.33	7.707%	$199.6134	$199.61	$199.60	$199.60
Purchase #4	$48.54	10.229%	$53.5052	$53.51	$53.50	$53.50
Purchase #5	$155.72	10.156%	$171.5349	$171.53	$171.55	$171.50
Purchase #6	$202.71	4.131%	$211.084	$211.08	$211.10	$211.10
Purchase #7	$159.81	8.609%	$173.568	$173.57	$173.55	$173.60
7 purchase totals =	$1,014.77		$1,098.3471	$1,098.35	$1,098.35	$1,098.40