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	$243.73	4.852%	$255.5558	$255.56	$255.55	$255.60
Purchase #2	$115.94	7.197%	$124.2842	$124.28	$124.30	$124.30
Purchase #3	$56.92	8.817%	$61.9386	$61.94	$61.95	$61.90
Purchase #4	$145.32	3.650%	$150.6242	$150.62	$150.60	$150.60
Purchase #5	$37.37	13.222%	$42.3111	$42.31	$42.30	$42.30
Purchase #6	$230.66	13.629%	$262.0967	$262.10	$262.10	$262.10
Purchase #7	$99.98	7.689%	$107.6675	$107.67	$107.65	$107.70
7 purchase totals =	$929.92		$1,004.4781	$1,004.48	$1,004.45	$1,004.50