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	$82.58	4.771%	$86.5199	$86.52	$86.50	$86.50
Purchase #2	$156.33	6.515%	$166.5149	$166.51	$166.50	$166.50
Purchase #3	$188.88	8.253%	$204.4683	$204.47	$204.45	$204.50
Purchase #4	$146.82	9.793%	$161.1981	$161.20	$161.20	$161.20
Purchase #5	$195.82	9.486%	$214.3955	$214.40	$214.40	$214.40
Purchase #6	$27.42	3.694%	$28.4329	$28.43	$28.45	$28.40
Purchase #7	$172.88	6.696%	$184.456	$184.46	$184.45	$184.50
7 purchase totals =	$970.73		$1,045.9856	$1,045.99	$1,045.95	$1,046.00