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	$214.46	5.188%	$225.5862	$225.59	$225.60	$225.60
Purchase #2	$189.77	12.263%	$213.0415	$213.04	$213.05	$213.00
Purchase #3	$130.44	6.861%	$139.3895	$139.39	$139.40	$139.40
Purchase #4	$151.94	5.235%	$159.8941	$159.89	$159.90	$159.90
Purchase #5	$72.40	13.175%	$81.9387	$81.94	$81.95	$81.90
Purchase #6	$200.99	8.188%	$217.4471	$217.45	$217.45	$217.40
Purchase #7	$104.62	6.333%	$111.2456	$111.25	$111.25	$111.20
7 purchase totals =	$1,064.62		$1,148.5427	$1,148.55	$1,148.60	$1,148.40