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	$67.82	3.486%	$70.1842	$70.18	$70.20	$70.20
Purchase #2	$170.56	6.415%	$181.5014	$181.50	$181.50	$181.50
Purchase #3	$128.83	13.743%	$146.5351	$146.54	$146.55	$146.50
Purchase #4	$239.50	8.499%	$259.8551	$259.86	$259.85	$259.90
Purchase #5	$222.31	11.256%	$247.3332	$247.33	$247.35	$247.30
Purchase #6	$31.99	3.832%	$33.2159	$33.22	$33.20	$33.20
Purchase #7	$148.72	4.777%	$155.8244	$155.82	$155.80	$155.80
7 purchase totals =	$1,009.73		$1,094.4493	$1,094.45	$1,094.45	$1,094.40