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	$135.34	11.659%	$151.1193	$151.12	$151.10	$151.10
Purchase #2	$96.44	13.319%	$109.2848	$109.28	$109.30	$109.30
Purchase #3	$220.42	11.389%	$245.5236	$245.52	$245.50	$245.50
Purchase #4	$176.29	11.711%	$196.9353	$196.94	$196.95	$196.90
Purchase #5	$125.96	5.363%	$132.7152	$132.72	$132.70	$132.70
Purchase #6	$239.70	11.522%	$267.3182	$267.32	$267.30	$267.30
Purchase #7	$154.40	4.755%	$161.7417	$161.74	$161.75	$161.70
7 purchase totals =	$1,148.55		$1,264.6381	$1,264.64	$1,264.60	$1,264.50