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	$185.91	11.281%	$206.8825	$206.88	$206.90	$206.90
Purchase #2	$161.96	10.135%	$178.3746	$178.37	$178.35	$178.40
Purchase #3	$44.80	7.759%	$48.276	$48.28	$48.30	$48.30
Purchase #4	$147.51	6.114%	$156.5288	$156.53	$156.55	$156.50
Purchase #5	$84.29	7.600%	$90.696	$90.70	$90.70	$90.70
Purchase #6	$90.63	11.127%	$100.7144	$100.71	$100.70	$100.70
Purchase #7	$250.30	8.447%	$271.4428	$271.44	$271.45	$271.40
7 purchase totals =	$965.40		$1,052.9151	$1,052.91	$1,052.95	$1,052.90