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	$200.98	13.561%	$228.2349	$228.23	$228.25	$228.20
Purchase #2	$216.35	5.765%	$228.8226	$228.82	$228.80	$228.80
Purchase #3	$175.85	11.398%	$195.8934	$195.89	$195.90	$195.90
Purchase #4	$173.72	3.118%	$179.1366	$179.14	$179.15	$179.10
Purchase #5	$93.40	8.849%	$101.665	$101.67	$101.65	$101.70
Purchase #6	$211.82	10.652%	$234.3831	$234.38	$234.40	$234.40
Purchase #7	$52.65	3.870%	$54.6876	$54.69	$54.70	$54.70
7 purchase totals =	$1,124.77		$1,222.8232	$1,222.82	$1,222.85	$1,222.80