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	$193.53	3.693%	$200.6771	$200.68	$200.70	$200.70
Purchase #2	$233.36	13.507%	$264.8799	$264.88	$264.90	$264.90
Purchase #3	$225.62	13.516%	$256.1148	$256.11	$256.10	$256.10
Purchase #4	$223.70	13.663%	$254.2641	$254.26	$254.25	$254.30
Purchase #5	$127.42	10.288%	$140.529	$140.53	$140.55	$140.50
Purchase #6	$174.79	9.442%	$191.2937	$191.29	$191.30	$191.30
Purchase #7	$130.74	8.389%	$141.7078	$141.71	$141.70	$141.70
7 purchase totals =	$1,309.16		$1,449.4664	$1,449.46	$1,449.50	$1,449.50