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	$131.32	4.634%	$137.4054	$137.41	$137.40	$137.40
Purchase #2	$169.50	7.117%	$181.5633	$181.56	$181.55	$181.60
Purchase #3	$46.40	13.461%	$52.6459	$52.65	$52.65	$52.60
Purchase #4	$201.32	3.481%	$208.3279	$208.33	$208.35	$208.30
Purchase #5	$103.65	4.612%	$108.4303	$108.43	$108.45	$108.40
Purchase #6	$169.77	11.349%	$189.0372	$189.04	$189.05	$189.00
Purchase #7	$238.56	12.166%	$267.5832	$267.58	$267.60	$267.60
7 purchase totals =	$1,060.52		$1,144.9932	$1,145.00	$1,145.05	$1,144.90