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	$145.77	4.618%	$152.5017	$152.50	$152.50	$152.50
Purchase #2	$238.72	4.783%	$250.138	$250.14	$250.15	$250.10
Purchase #3	$227.47	5.800%	$240.6633	$240.66	$240.65	$240.70
Purchase #4	$183.37	10.727%	$203.0401	$203.04	$203.05	$203.00
Purchase #5	$26.91	7.373%	$28.8941	$28.89	$28.90	$28.90
Purchase #6	$94.50	13.762%	$107.5051	$107.51	$107.50	$107.50
Purchase #7	$149.72	10.394%	$165.2819	$165.28	$165.30	$165.30
7 purchase totals =	$1,066.46		$1,148.0242	$1,148.02	$1,148.05	$1,148.00