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	$103.74	7.791%	$111.8224	$111.82	$111.80	$111.80
Purchase #2	$137.36	10.334%	$151.5548	$151.55	$151.55	$151.60
Purchase #3	$53.70	3.282%	$55.4624	$55.46	$55.45	$55.50
Purchase #4	$230.71	8.551%	$250.438	$250.44	$250.45	$250.40
Purchase #5	$243.55	13.529%	$276.4999	$276.50	$276.50	$276.50
Purchase #6	$44.38	3.410%	$45.8934	$45.89	$45.90	$45.90
Purchase #7	$185.65	13.846%	$211.3551	$211.36	$211.35	$211.40
7 purchase totals =	$999.09		$1,103.0260	$1,103.02	$1,103.00	$1,103.10