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	$190.84	5.300%	$200.9545	$200.95	$200.95	$201.00
Purchase #2	$150.50	4.275%	$156.9339	$156.93	$156.95	$156.90
Purchase #3	$118.78	7.286%	$127.4343	$127.43	$127.45	$127.40
Purchase #4	$118.82	9.310%	$129.8821	$129.88	$129.90	$129.90
Purchase #5	$123.93	13.560%	$140.7349	$140.73	$140.75	$140.70
Purchase #6	$45.98	13.490%	$52.1827	$52.18	$52.20	$52.20
Purchase #7	$88.54	8.180%	$95.7826	$95.78	$95.80	$95.80
7 purchase totals =	$837.39		$903.9050	$903.88	$904.00	$903.90