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	$136.26	5.447%	$143.6821	$143.68	$143.70	$143.70
Purchase #2	$133.84	13.817%	$152.3327	$152.33	$152.35	$152.30
Purchase #3	$43.52	8.395%	$47.1735	$47.17	$47.15	$47.20
Purchase #4	$170.67	10.600%	$188.761	$188.76	$188.75	$188.80
Purchase #5	$59.91	7.475%	$64.3883	$64.39	$64.40	$64.40
Purchase #6	$59.53	4.830%	$62.4053	$62.41	$62.40	$62.40
Purchase #7	$239.64	6.760%	$255.8397	$255.84	$255.85	$255.80
7 purchase totals =	$843.37		$914.5826	$914.58	$914.60	$914.60