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	$226.46	9.142%	$247.163	$247.16	$247.15	$247.20
Purchase #2	$132.55	6.815%	$141.5833	$141.58	$141.60	$141.60
Purchase #3	$80.73	6.226%	$85.7562	$85.76	$85.75	$85.80
Purchase #4	$14.89	3.870%	$15.4662	$15.47	$15.45	$15.50
Purchase #5	$200.50	9.403%	$219.353	$219.35	$219.35	$219.40
Purchase #6	$34.69	13.171%	$39.259	$39.26	$39.25	$39.30
Purchase #7	$98.69	6.562%	$105.166	$105.17	$105.15	$105.20
7 purchase totals =	$788.51		$853.7467	$853.75	$853.70	$854.00