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	$197.96	9.814%	$217.3878	$217.39	$217.40	$217.40
Purchase #2	$48.46	11.801%	$54.1788	$54.18	$54.20	$54.20
Purchase #3	$106.63	8.771%	$115.9825	$115.98	$116.00	$116.00
Purchase #4	$117.90	11.331%	$131.2592	$131.26	$131.25	$131.30
Purchase #5	$227.95	6.702%	$243.2272	$243.23	$243.25	$243.20
Purchase #6	$61.83	9.426%	$67.6581	$67.66	$67.65	$67.70
Purchase #7	$131.53	12.811%	$148.3803	$148.38	$148.40	$148.40
7 purchase totals =	$892.26		$978.0739	$978.08	$978.15	$978.20