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	$104.50	7.150%	$111.9718	$111.97	$111.95	$112.00
Purchase #2	$222.47	5.733%	$235.2242	$235.22	$235.20	$235.20
Purchase #3	$123.63	6.339%	$131.4669	$131.47	$131.45	$131.50
Purchase #4	$93.89	3.144%	$96.8419	$96.84	$96.85	$96.80
Purchase #5	$29.65	5.119%	$31.1678	$31.17	$31.15	$31.20
Purchase #6	$28.45	10.289%	$31.3772	$31.38	$31.40	$31.40
Purchase #7	$100.33	12.753%	$113.1251	$113.13	$113.15	$113.10
7 purchase totals =	$702.92		$751.1749	$751.18	$751.15	$751.20