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	$46.51	13.797%	$52.927	$52.93	$52.95	$52.90
Purchase #2	$55.65	7.120%	$59.6123	$59.61	$59.60	$59.60
Purchase #3	$24.25	12.475%	$27.2752	$27.28	$27.30	$27.30
Purchase #4	$118.63	12.117%	$133.0044	$133.00	$133.00	$133.00
Purchase #5	$213.52	4.595%	$223.3312	$223.33	$223.35	$223.30
Purchase #6	$82.30	13.669%	$93.5496	$93.55	$93.55	$93.50
Purchase #7	$37.61	10.485%	$41.5534	$41.55	$41.55	$41.60
7 purchase totals =	$578.47		$631.2531	$631.25	$631.30	$631.20