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	$194.90	8.160%	$210.8038	$210.80	$210.80	$210.80
Purchase #2	$145.42	10.343%	$160.4608	$160.46	$160.45	$160.50
Purchase #3	$119.41	11.856%	$133.5672	$133.57	$133.55	$133.60
Purchase #4	$160.50	3.131%	$165.5253	$165.53	$165.55	$165.50
Purchase #5	$57.59	9.102%	$62.8318	$62.83	$62.85	$62.80
Purchase #6	$39.92	6.284%	$42.4286	$42.43	$42.45	$42.40
Purchase #7	$162.27	6.317%	$172.5206	$172.52	$172.50	$172.50
7 purchase totals =	$880.01		$948.1381	$948.14	$948.15	$948.10