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	$57.54	4.733%	$60.2634	$60.26	$60.25	$60.30
Purchase #2	$150.97	3.824%	$156.7431	$156.74	$156.75	$156.70
Purchase #3	$118.99	3.787%	$123.4962	$123.50	$123.50	$123.50
Purchase #4	$237.82	13.643%	$270.2658	$270.27	$270.25	$270.30
Purchase #5	$68.61	12.740%	$77.3509	$77.35	$77.35	$77.40
Purchase #6	$209.34	9.105%	$228.4004	$228.40	$228.40	$228.40
Purchase #7	$85.61	7.804%	$92.291	$92.29	$92.30	$92.30
7 purchase totals =	$928.88		$1,008.8108	$1,008.81	$1,008.80	$1,008.90