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	$216.88	6.294%	$230.5304	$230.53	$230.55	$230.50
Purchase #2	$187.69	9.491%	$205.5037	$205.50	$205.50	$205.50
Purchase #3	$147.79	3.211%	$152.5355	$152.54	$152.55	$152.50
Purchase #4	$232.45	13.529%	$263.8982	$263.90	$263.90	$263.90
Purchase #5	$77.42	7.749%	$83.4193	$83.42	$83.40	$83.40
Purchase #6	$89.45	5.384%	$94.266	$94.27	$94.25	$94.30
Purchase #7	$64.74	12.791%	$73.0209	$73.02	$73.00	$73.00
7 purchase totals =	$1,016.42		$1,103.1740	$1,103.18	$1,103.15	$1,103.10