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	$81.32	11.182%	$90.4132	$90.41	$90.40	$90.40
Purchase #2	$149.33	13.568%	$169.5911	$169.59	$169.60	$169.60
Purchase #3	$121.27	7.642%	$130.5375	$130.54	$130.55	$130.50
Purchase #4	$169.83	6.327%	$180.5751	$180.58	$180.60	$180.60
Purchase #5	$176.29	3.574%	$182.5906	$182.59	$182.60	$182.60
Purchase #6	$173.82	9.540%	$190.4024	$190.40	$190.40	$190.40
Purchase #7	$231.60	8.159%	$250.4962	$250.50	$250.50	$250.50
7 purchase totals =	$1,103.46		$1,194.6061	$1,194.61	$1,194.65	$1,194.60