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	$209.55	4.310%	$218.5816	$218.58	$218.60	$218.60
Purchase #2	$184.76	10.459%	$204.084	$204.08	$204.10	$204.10
Purchase #3	$50.42	4.274%	$52.575	$52.58	$52.60	$52.60
Purchase #4	$146.65	13.117%	$165.8861	$165.89	$165.90	$165.90
Purchase #5	$37.58	6.377%	$39.9765	$39.98	$40.00	$40.00
Purchase #6	$185.69	7.527%	$199.6669	$199.67	$199.65	$199.70
Purchase #7	$130.78	9.208%	$142.8222	$142.82	$142.80	$142.80
7 purchase totals =	$945.43		$1,023.5923	$1,023.60	$1,023.65	$1,023.70