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	$114.32	13.833%	$130.1339	$130.13	$130.15	$130.10
Purchase #2	$92.61	11.822%	$103.5584	$103.56	$103.55	$103.60
Purchase #3	$245.91	4.121%	$256.044	$256.04	$256.05	$256.00
Purchase #4	$143.36	4.170%	$149.3381	$149.34	$149.35	$149.30
Purchase #5	$134.46	7.272%	$144.2379	$144.24	$144.25	$144.20
Purchase #6	$172.50	7.628%	$185.6583	$185.66	$185.65	$185.70
Purchase #7	$115.37	8.107%	$124.723	$124.72	$124.70	$124.70
7 purchase totals =	$1,018.53		$1,093.6936	$1,093.69	$1,093.70	$1,093.60