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	$78.95	11.490%	$88.0214	$88.02	$88.00	$88.00
Purchase #2	$144.50	5.317%	$152.1831	$152.18	$152.20	$152.20
Purchase #3	$155.67	6.525%	$165.8275	$165.83	$165.85	$165.80
Purchase #4	$225.74	10.609%	$249.6888	$249.69	$249.70	$249.70
Purchase #5	$56.88	8.165%	$61.5243	$61.52	$61.50	$61.50
Purchase #6	$198.58	4.865%	$208.2409	$208.24	$208.25	$208.20
Purchase #7	$79.51	9.339%	$86.9354	$86.94	$86.95	$86.90
7 purchase totals =	$939.83		$1,012.4214	$1,012.42	$1,012.45	$1,012.30