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	$88.50	8.275%	$95.8234	$95.82	$95.80	$95.80
Purchase #2	$63.82	13.475%	$72.4197	$72.42	$72.40	$72.40
Purchase #3	$201.59	11.654%	$225.0833	$225.08	$225.10	$225.10
Purchase #4	$189.50	9.820%	$208.1089	$208.11	$208.10	$208.10
Purchase #5	$61.94	13.852%	$70.5199	$70.52	$70.50	$70.50
Purchase #6	$71.46	12.276%	$80.2324	$80.23	$80.25	$80.20
Purchase #7	$197.58	13.477%	$224.2079	$224.21	$224.20	$224.20
7 purchase totals =	$874.39		$976.3955	$976.39	$976.35	$976.30