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	$182.81	4.640%	$191.2924	$191.29	$191.30	$191.30
Purchase #2	$33.51	7.141%	$35.9029	$35.90	$35.90	$35.90
Purchase #3	$110.54	10.154%	$121.7642	$121.76	$121.75	$121.80
Purchase #4	$83.87	7.309%	$90.0001	$90.00	$90.00	$90.00
Purchase #5	$215.71	10.358%	$238.0532	$238.05	$238.05	$238.10
Purchase #6	$180.90	9.580%	$198.2302	$198.23	$198.25	$198.20
Purchase #7	$29.41	9.670%	$32.2539	$32.25	$32.25	$32.30
7 purchase totals =	$836.75		$907.4969	$907.48	$907.50	$907.60