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	$230.85	9.550%	$252.8962	$252.90	$252.90	$252.90
Purchase #2	$62.66	8.169%	$67.7787	$67.78	$67.80	$67.80
Purchase #3	$174.69	6.145%	$185.4247	$185.42	$185.40	$185.40
Purchase #4	$66.48	5.524%	$70.1524	$70.15	$70.15	$70.20
Purchase #5	$144.29	8.349%	$156.3368	$156.34	$156.35	$156.30
Purchase #6	$247.60	3.521%	$256.318	$256.32	$256.30	$256.30
Purchase #7	$76.39	9.464%	$83.6195	$83.62	$83.60	$83.60
7 purchase totals =	$1,002.96		$1,072.5263	$1,072.53	$1,072.50	$1,072.50