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	$88.94	3.817%	$92.3348	$92.33	$92.35	$92.30
Purchase #2	$65.52	11.671%	$73.1668	$73.17	$73.15	$73.20
Purchase #3	$244.26	3.689%	$253.2708	$253.27	$253.25	$253.30
Purchase #4	$17.74	9.710%	$19.4626	$19.46	$19.45	$19.50
Purchase #5	$178.46	12.594%	$200.9353	$200.94	$200.95	$200.90
Purchase #6	$55.27	4.139%	$57.5576	$57.56	$57.55	$57.60
Purchase #7	$98.29	13.405%	$111.4658	$111.47	$111.45	$111.50
7 purchase totals =	$748.48		$808.1937	$808.20	$808.15	$808.30