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	$230.91	7.342%	$247.8634	$247.86	$247.85	$247.90
Purchase #2	$83.60	8.160%	$90.4218	$90.42	$90.40	$90.40
Purchase #3	$69.96	4.114%	$72.8382	$72.84	$72.85	$72.80
Purchase #4	$234.55	4.797%	$245.8014	$245.80	$245.80	$245.80
Purchase #5	$87.55	13.463%	$99.3369	$99.34	$99.35	$99.30
Purchase #6	$37.53	10.838%	$41.5975	$41.60	$41.60	$41.60
Purchase #7	$136.76	9.325%	$149.5129	$149.51	$149.50	$149.50
7 purchase totals =	$880.86		$947.3721	$947.37	$947.35	$947.30