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	$113.30	9.853%	$124.4634	$124.46	$124.45	$124.50
Purchase #2	$160.57	5.718%	$169.7514	$169.75	$169.75	$169.80
Purchase #3	$195.64	9.279%	$213.7934	$213.79	$213.80	$213.80
Purchase #4	$216.33	3.439%	$223.7696	$223.77	$223.75	$223.80
Purchase #5	$52.77	12.429%	$59.3288	$59.33	$59.35	$59.30
Purchase #6	$246.98	8.350%	$267.6028	$267.60	$267.60	$267.60
Purchase #7	$26.64	7.414%	$28.6151	$28.62	$28.60	$28.60
7 purchase totals =	$1,012.23		$1,087.3245	$1,087.32	$1,087.30	$1,087.40