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	$46.60	11.826%	$52.1109	$52.11	$52.10	$52.10
Purchase #2	$61.84	8.872%	$67.3264	$67.33	$67.35	$67.30
Purchase #3	$92.50	6.767%	$98.7595	$98.76	$98.75	$98.80
Purchase #4	$37.53	9.346%	$41.0376	$41.04	$41.05	$41.00
Purchase #5	$18.32	4.495%	$19.1435	$19.14	$19.15	$19.10
Purchase #6	$138.39	8.843%	$150.6278	$150.63	$150.65	$150.60
Purchase #7	$70.47	9.134%	$76.9067	$76.91	$76.90	$76.90
7 purchase totals =	$465.65		$505.9124	$505.92	$505.95	$505.80