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	$53.47	11.784%	$59.7709	$59.77	$59.75	$59.80
Purchase #2	$115.35	3.669%	$119.5822	$119.58	$119.60	$119.60
Purchase #3	$75.56	13.307%	$85.6148	$85.61	$85.60	$85.60
Purchase #4	$176.50	12.334%	$198.2695	$198.27	$198.25	$198.30
Purchase #5	$223.80	11.756%	$250.1099	$250.11	$250.10	$250.10
Purchase #6	$131.27	10.220%	$144.6858	$144.69	$144.70	$144.70
Purchase #7	$137.48	9.623%	$150.7097	$150.71	$150.70	$150.70
7 purchase totals =	$913.43		$1,008.7428	$1,008.74	$1,008.70	$1,008.80