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	$38.73	6.674%	$41.3148	$41.31	$41.30	$41.30
Purchase #2	$249.76	6.268%	$265.415	$265.42	$265.40	$265.40
Purchase #3	$145.53	4.510%	$152.0934	$152.09	$152.10	$152.10
Purchase #4	$77.47	5.170%	$81.4752	$81.48	$81.50	$81.50
Purchase #5	$34.27	8.691%	$37.2484	$37.25	$37.25	$37.20
Purchase #6	$98.52	6.267%	$104.6942	$104.69	$104.70	$104.70
Purchase #7	$115.53	6.733%	$123.3086	$123.31	$123.30	$123.30
7 purchase totals =	$759.81		$805.5496	$805.55	$805.55	$805.50