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	$57.33	4.411%	$59.8588	$59.86	$59.85	$59.90
Purchase #2	$221.66	13.606%	$251.8191	$251.82	$251.80	$251.80
Purchase #3	$53.29	9.475%	$58.3392	$58.34	$58.35	$58.30
Purchase #4	$25.30	12.315%	$28.4157	$28.42	$28.40	$28.40
Purchase #5	$73.93	12.429%	$83.1188	$83.12	$83.10	$83.10
Purchase #6	$234.61	8.339%	$254.1741	$254.17	$254.15	$254.20
Purchase #7	$29.30	11.352%	$32.6261	$32.63	$32.65	$32.60
7 purchase totals =	$695.42		$768.3518	$768.36	$768.30	$768.30