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	$30.39	11.392%	$33.852	$33.85	$33.85	$33.90
Purchase #2	$152.42	10.789%	$168.8646	$168.86	$168.85	$168.90
Purchase #3	$232.55	5.306%	$244.8891	$244.89	$244.90	$244.90
Purchase #4	$155.38	9.108%	$169.532	$169.53	$169.55	$169.50
Purchase #5	$136.81	5.115%	$143.8078	$143.81	$143.80	$143.80
Purchase #6	$147.45	7.332%	$158.261	$158.26	$158.25	$158.30
Purchase #7	$185.98	5.602%	$196.3986	$196.40	$196.40	$196.40
7 purchase totals =	$1,040.98		$1,115.6051	$1,115.60	$1,115.60	$1,115.70