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	$52.70	3.153%	$54.3616	$54.36	$54.35	$54.40
Purchase #2	$83.55	5.487%	$88.1344	$88.13	$88.15	$88.10
Purchase #3	$52.89	11.635%	$59.0438	$59.04	$59.05	$59.00
Purchase #4	$61.39	11.844%	$68.661	$68.66	$68.65	$68.70
Purchase #5	$103.39	13.770%	$117.6268	$117.63	$117.65	$117.60
Purchase #6	$34.98	6.224%	$37.1572	$37.16	$37.15	$37.20
Purchase #7	$165.63	9.124%	$180.7421	$180.74	$180.75	$180.70
7 purchase totals =	$554.53		$605.7269	$605.72	$605.75	$605.70