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	$106.50	3.150%	$109.8548	$109.85	$109.85	$109.90
Purchase #2	$33.46	8.516%	$36.3095	$36.31	$36.30	$36.30
Purchase #3	$104.44	8.816%	$113.6474	$113.65	$113.65	$113.60
Purchase #4	$113.58	13.466%	$128.8747	$128.87	$128.85	$128.90
Purchase #5	$147.95	11.858%	$165.4939	$165.49	$165.50	$165.50
Purchase #6	$92.89	12.104%	$104.1334	$104.13	$104.15	$104.10
Purchase #7	$114.59	7.864%	$123.6014	$123.60	$123.60	$123.60
7 purchase totals =	$713.41		$781.9151	$781.90	$781.90	$781.90