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	$203.55	13.675%	$231.3855	$231.39	$231.40	$231.40
Purchase #2	$242.75	7.845%	$261.7937	$261.79	$261.80	$261.80
Purchase #3	$55.57	10.779%	$61.5599	$61.56	$61.55	$61.60
Purchase #4	$175.47	5.807%	$185.6595	$185.66	$185.65	$185.70
Purchase #5	$37.58	11.861%	$42.0374	$42.04	$42.05	$42.00
Purchase #6	$39.93	10.527%	$44.1334	$44.13	$44.15	$44.10
Purchase #7	$200.63	11.519%	$223.7406	$223.74	$223.75	$223.70
7 purchase totals =	$955.48		$1,050.3100	$1,050.31	$1,050.35	$1,050.30