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	$148.88	7.641%	$160.2559	$160.26	$160.25	$160.30
Purchase #2	$199.39	9.862%	$219.0538	$219.05	$219.05	$219.10
Purchase #3	$130.29	9.155%	$142.218	$142.22	$142.20	$142.20
Purchase #4	$105.85	13.154%	$119.7735	$119.77	$119.75	$119.80
Purchase #5	$213.44	10.125%	$235.0508	$235.05	$235.05	$235.10
Purchase #6	$197.35	12.674%	$222.3621	$222.36	$222.35	$222.40
Purchase #7	$80.32	12.698%	$90.519	$90.52	$90.50	$90.50
7 purchase totals =	$1,075.52		$1,189.2331	$1,189.23	$1,189.15	$1,189.40