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	$174.40	8.234%	$188.7601	$188.76	$188.75	$188.80
Purchase #2	$113.35	12.512%	$127.5324	$127.53	$127.55	$127.50
Purchase #3	$11.98	8.477%	$12.9955	$13.00	$13.00	$13.00
Purchase #4	$177.35	7.619%	$190.8623	$190.86	$190.85	$190.90
Purchase #5	$12.74	12.797%	$14.3703	$14.37	$14.35	$14.40
Purchase #6	$130.32	13.693%	$148.1647	$148.16	$148.15	$148.20
Purchase #7	$47.32	12.723%	$53.3405	$53.34	$53.35	$53.30
7 purchase totals =	$667.46		$736.0258	$736.02	$736.00	$736.10