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	$198.33	8.131%	$214.4562	$214.46	$214.45	$214.50
Purchase #2	$188.29	6.655%	$200.8207	$200.82	$200.80	$200.80
Purchase #3	$26.73	3.742%	$27.7302	$27.73	$27.75	$27.70
Purchase #4	$80.33	7.709%	$86.5226	$86.52	$86.50	$86.50
Purchase #5	$55.96	7.733%	$60.2874	$60.29	$60.30	$60.30
Purchase #6	$35.30	12.449%	$39.6945	$39.69	$39.70	$39.70
Purchase #7	$173.37	4.119%	$180.5111	$180.51	$180.50	$180.50
7 purchase totals =	$758.31		$810.0227	$810.02	$810.00	$810.00