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	$161.64	4.258%	$168.5226	$168.52	$168.50	$168.50
Purchase #2	$11.51	6.523%	$12.2608	$12.26	$12.25	$12.30
Purchase #3	$121.73	7.865%	$131.3041	$131.30	$131.30	$131.30
Purchase #4	$245.32	9.805%	$269.3736	$269.37	$269.35	$269.40
Purchase #5	$94.33	10.785%	$104.5035	$104.50	$104.50	$104.50
Purchase #6	$129.25	11.217%	$143.748	$143.75	$143.75	$143.70
Purchase #7	$37.30	12.179%	$41.8428	$41.84	$41.85	$41.80
7 purchase totals =	$801.08		$871.5554	$871.54	$871.50	$871.50