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	$227.89	10.509%	$251.839	$251.84	$251.85	$251.80
Purchase #2	$35.41	5.428%	$37.3321	$37.33	$37.35	$37.30
Purchase #3	$171.98	10.166%	$189.4635	$189.46	$189.45	$189.50
Purchase #4	$78.30	4.501%	$81.8243	$81.82	$81.80	$81.80
Purchase #5	$197.47	10.294%	$217.7976	$217.80	$217.80	$217.80
Purchase #6	$212.26	10.492%	$234.5303	$234.53	$234.55	$234.50
Purchase #7	$79.44	4.632%	$83.1197	$83.12	$83.10	$83.10
7 purchase totals =	$1,002.75		$1,095.9065	$1,095.90	$1,095.90	$1,095.80