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	$226.35	11.715%	$252.8669	$252.87	$252.85	$252.90
Purchase #2	$43.51	3.576%	$45.0659	$45.07	$45.05	$45.10
Purchase #3	$55.83	7.314%	$59.9134	$59.91	$59.90	$59.90
Purchase #4	$53.86	7.447%	$57.871	$57.87	$57.85	$57.90
Purchase #5	$245.46	12.508%	$276.1621	$276.16	$276.15	$276.20
Purchase #6	$86.75	13.567%	$98.5194	$98.52	$98.50	$98.50
Purchase #7	$129.46	12.146%	$145.1842	$145.18	$145.20	$145.20
7 purchase totals =	$841.22		$935.5829	$935.58	$935.50	$935.70