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	$188.84	12.521%	$212.4847	$212.48	$212.50	$212.50
Purchase #2	$71.50	7.375%	$76.7731	$76.77	$76.75	$76.80
Purchase #3	$126.82	7.367%	$136.1628	$136.16	$136.15	$136.20
Purchase #4	$62.44	6.392%	$66.4312	$66.43	$66.45	$66.40
Purchase #5	$172.40	7.710%	$185.692	$185.69	$185.70	$185.70
Purchase #6	$47.46	12.852%	$53.5596	$53.56	$53.55	$53.60
Purchase #7	$145.82	6.481%	$155.2706	$155.27	$155.25	$155.30
7 purchase totals =	$815.28		$886.3740	$886.36	$886.35	$886.50