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	$208.65	12.267%	$234.2451	$234.25	$234.25	$234.20
Purchase #2	$173.43	10.809%	$192.176	$192.18	$192.20	$192.20
Purchase #3	$145.56	10.487%	$160.8249	$160.82	$160.80	$160.80
Purchase #4	$67.30	9.122%	$73.4391	$73.44	$73.45	$73.40
Purchase #5	$78.39	6.317%	$83.3419	$83.34	$83.35	$83.30
Purchase #6	$197.29	5.872%	$208.8749	$208.87	$208.85	$208.90
Purchase #7	$82.48	9.308%	$90.1572	$90.16	$90.15	$90.20
7 purchase totals =	$953.10		$1,043.0591	$1,043.06	$1,043.05	$1,043.00