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	$98.65	7.202%	$105.7548	$105.75	$105.75	$105.80
Purchase #2	$215.89	5.148%	$227.004	$227.00	$227.00	$227.00
Purchase #3	$245.89	13.634%	$279.4146	$279.41	$279.40	$279.40
Purchase #4	$148.57	13.864%	$169.1677	$169.17	$169.15	$169.20
Purchase #5	$30.60	9.618%	$33.5431	$33.54	$33.55	$33.50
Purchase #6	$29.99	5.294%	$31.5777	$31.58	$31.60	$31.60
Purchase #7	$141.44	10.839%	$156.7707	$156.77	$156.75	$156.80
7 purchase totals =	$911.03		$1,003.2326	$1,003.22	$1,003.20	$1,003.30