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	$174.41	8.605%	$189.418	$189.42	$189.40	$189.40
Purchase #2	$165.44	13.557%	$187.8687	$187.87	$187.85	$187.90
Purchase #3	$200.40	7.814%	$216.0593	$216.06	$216.05	$216.10
Purchase #4	$53.82	7.490%	$57.8511	$57.85	$57.85	$57.90
Purchase #5	$228.86	6.475%	$243.6787	$243.68	$243.70	$243.70
Purchase #6	$60.94	10.281%	$67.2052	$67.21	$67.20	$67.20
Purchase #7	$123.79	11.808%	$138.4071	$138.41	$138.40	$138.40
7 purchase totals =	$1,007.66		$1,100.4881	$1,100.50	$1,100.45	$1,100.60