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	$58.72	4.607%	$61.4252	$61.43	$61.45	$61.40
Purchase #2	$193.64	13.632%	$220.037	$220.04	$220.05	$220.00
Purchase #3	$64.91	11.552%	$72.4084	$72.41	$72.40	$72.40
Purchase #4	$87.49	3.465%	$90.5215	$90.52	$90.50	$90.50
Purchase #5	$36.60	5.153%	$38.486	$38.49	$38.50	$38.50
Purchase #6	$99.30	5.510%	$104.7714	$104.77	$104.75	$104.80
Purchase #7	$218.43	13.246%	$247.3632	$247.36	$247.35	$247.40
7 purchase totals =	$759.09		$835.0127	$835.02	$835.00	$835.00