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	$43.58	6.637%	$46.4724	$46.47	$46.45	$46.50
Purchase #2	$240.64	13.215%	$272.4406	$272.44	$272.45	$272.40
Purchase #3	$122.48	12.445%	$137.7226	$137.72	$137.70	$137.70
Purchase #4	$130.83	10.756%	$144.9021	$144.90	$144.90	$144.90
Purchase #5	$147.56	7.443%	$158.5429	$158.54	$158.55	$158.50
Purchase #6	$155.35	6.623%	$165.6388	$165.64	$165.65	$165.60
Purchase #7	$202.32	8.257%	$219.0256	$219.03	$219.05	$219.00
7 purchase totals =	$1,042.76		$1,144.7450	$1,144.74	$1,144.75	$1,144.60