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	$141.59	6.620%	$150.9633	$150.96	$150.95	$151.00
Purchase #2	$139.60	6.390%	$148.5204	$148.52	$148.50	$148.50
Purchase #3	$173.44	13.527%	$196.9012	$196.90	$196.90	$196.90
Purchase #4	$110.76	3.309%	$114.425	$114.43	$114.45	$114.40
Purchase #5	$58.55	9.575%	$64.1562	$64.16	$64.15	$64.20
Purchase #6	$55.88	9.568%	$61.2266	$61.23	$61.25	$61.20
Purchase #7	$204.83	10.517%	$226.372	$226.37	$226.35	$226.40
7 purchase totals =	$884.65		$962.5647	$962.57	$962.55	$962.60