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	$166.55	5.386%	$175.5204	$175.52	$175.50	$175.50
Purchase #2	$148.30	5.714%	$156.7739	$156.77	$156.75	$156.80
Purchase #3	$144.65	4.763%	$151.5397	$151.54	$151.55	$151.50
Purchase #4	$64.75	4.779%	$67.8444	$67.84	$67.85	$67.80
Purchase #5	$167.90	8.429%	$182.0523	$182.05	$182.05	$182.10
Purchase #6	$121.95	7.314%	$130.8694	$130.87	$130.85	$130.90
Purchase #7	$232.44	9.433%	$254.3661	$254.37	$254.35	$254.40
7 purchase totals =	$1,046.54		$1,118.9662	$1,118.96	$1,118.90	$1,119.00