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	$100.43	7.574%	$108.0366	$108.04	$108.05	$108.00
Purchase #2	$12.73	13.829%	$14.4904	$14.49	$14.50	$14.50
Purchase #3	$123.68	13.566%	$140.4584	$140.46	$140.45	$140.50
Purchase #4	$130.95	10.739%	$145.0127	$145.01	$145.00	$145.00
Purchase #5	$165.59	5.576%	$174.8233	$174.82	$174.80	$174.80
Purchase #6	$175.31	4.154%	$182.5924	$182.59	$182.60	$182.60
Purchase #7	$200.43	5.494%	$211.4416	$211.44	$211.45	$211.40
7 purchase totals =	$909.12		$976.8554	$976.85	$976.85	$976.80