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	$141.48	7.103%	$151.5293	$151.53	$151.55	$151.50
Purchase #2	$29.37	11.214%	$32.6636	$32.66	$32.65	$32.70
Purchase #3	$88.78	5.393%	$93.5679	$93.57	$93.55	$93.60
Purchase #4	$12.74	4.172%	$13.2715	$13.27	$13.25	$13.30
Purchase #5	$27.67	4.270%	$28.8515	$28.85	$28.85	$28.90
Purchase #6	$144.86	7.501%	$155.7259	$155.73	$155.75	$155.70
Purchase #7	$108.41	3.694%	$112.4147	$112.41	$112.40	$112.40
7 purchase totals =	$553.31		$588.0244	$588.02	$588.00	$588.10