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	$195.34	12.315%	$219.3961	$219.40	$219.40	$219.40
Purchase #2	$16.69	8.518%	$18.1117	$18.11	$18.10	$18.10
Purchase #3	$240.58	10.700%	$266.3221	$266.32	$266.30	$266.30
Purchase #4	$80.60	11.837%	$90.1406	$90.14	$90.15	$90.10
Purchase #5	$68.86	12.828%	$77.6934	$77.69	$77.70	$77.70
Purchase #6	$80.31	13.124%	$90.8499	$90.85	$90.85	$90.80
Purchase #7	$249.43	8.186%	$269.8483	$269.85	$269.85	$269.80
7 purchase totals =	$931.81		$1,032.3621	$1,032.36	$1,032.35	$1,032.20