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	$134.54	13.147%	$152.228	$152.23	$152.25	$152.20
Purchase #2	$22.39	4.196%	$23.3295	$23.33	$23.35	$23.30
Purchase #3	$173.90	5.869%	$184.1062	$184.11	$184.10	$184.10
Purchase #4	$144.31	9.199%	$157.5851	$157.59	$157.60	$157.60
Purchase #5	$139.53	6.314%	$148.3399	$148.34	$148.35	$148.30
Purchase #6	$228.89	12.375%	$257.2151	$257.22	$257.20	$257.20
Purchase #7	$95.48	5.627%	$100.8527	$100.85	$100.85	$100.90
7 purchase totals =	$939.04		$1,023.6565	$1,023.67	$1,023.70	$1,023.60