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	$137.91	7.668%	$148.4849	$148.48	$148.50	$148.50
Purchase #2	$170.43	8.637%	$185.15	$185.15	$185.15	$185.20
Purchase #3	$133.85	8.238%	$144.8766	$144.88	$144.90	$144.90
Purchase #4	$101.97	9.501%	$111.6582	$111.66	$111.65	$111.70
Purchase #5	$94.57	5.106%	$99.3987	$99.40	$99.40	$99.40
Purchase #6	$114.67	5.637%	$121.1339	$121.13	$121.15	$121.10
Purchase #7	$234.42	9.387%	$256.425	$256.43	$256.45	$256.40
7 purchase totals =	$987.82		$1,067.1273	$1,067.13	$1,067.20	$1,067.20