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	$12.67	7.681%	$13.6432	$13.64	$13.65	$13.60
Purchase #2	$126.76	12.241%	$142.2767	$142.28	$142.30	$142.30
Purchase #3	$150.29	7.473%	$161.5212	$161.52	$161.50	$161.50
Purchase #4	$136.29	11.735%	$152.2836	$152.28	$152.30	$152.30
Purchase #5	$184.36	8.651%	$200.309	$200.31	$200.30	$200.30
Purchase #6	$166.50	11.407%	$185.4927	$185.49	$185.50	$185.50
Purchase #7	$244.58	4.411%	$255.3684	$255.37	$255.35	$255.40
7 purchase totals =	$1,021.45		$1,110.8948	$1,110.89	$1,110.90	$1,110.90