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	$113.34	4.350%	$118.2703	$118.27	$118.25	$118.30
Purchase #2	$97.56	6.710%	$104.1063	$104.11	$104.10	$104.10
Purchase #3	$98.76	12.731%	$111.3331	$111.33	$111.35	$111.30
Purchase #4	$104.82	10.797%	$116.1374	$116.14	$116.15	$116.10
Purchase #5	$195.63	8.254%	$211.7773	$211.78	$211.80	$211.80
Purchase #6	$199.95	12.198%	$224.3399	$224.34	$224.35	$224.30
Purchase #7	$48.72	9.262%	$53.2324	$53.23	$53.25	$53.20
7 purchase totals =	$858.78		$939.1967	$939.20	$939.25	$939.10