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	$23.43	4.686%	$24.5279	$24.53	$24.55	$24.50
Purchase #2	$89.56	6.598%	$95.4692	$95.47	$95.45	$95.50
Purchase #3	$50.41	13.518%	$57.2244	$57.22	$57.20	$57.20
Purchase #4	$80.86	10.814%	$89.6042	$89.60	$89.60	$89.60
Purchase #5	$179.65	6.334%	$191.029	$191.03	$191.05	$191.00
Purchase #6	$205.43	3.290%	$212.1886	$212.19	$212.20	$212.20
Purchase #7	$75.33	7.427%	$80.9248	$80.92	$80.90	$80.90
7 purchase totals =	$704.67		$750.9681	$750.96	$750.95	$750.90