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	$209.66	7.584%	$225.5606	$225.56	$225.55	$225.60
Purchase #2	$83.33	9.419%	$91.1789	$91.18	$91.20	$91.20
Purchase #3	$143.82	9.153%	$156.9838	$156.98	$157.00	$157.00
Purchase #4	$54.43	3.518%	$56.3448	$56.34	$56.35	$56.30
Purchase #5	$219.70	4.830%	$230.3115	$230.31	$230.30	$230.30
Purchase #6	$166.55	10.575%	$184.1627	$184.16	$184.15	$184.20
Purchase #7	$98.73	12.524%	$111.0949	$111.09	$111.10	$111.10
7 purchase totals =	$976.22		$1,055.6372	$1,055.62	$1,055.65	$1,055.70