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	$196.89	12.655%	$221.8064	$221.81	$221.80	$221.80
Purchase #2	$90.40	5.205%	$95.1053	$95.11	$95.10	$95.10
Purchase #3	$191.84	11.622%	$214.1356	$214.14	$214.15	$214.10
Purchase #4	$146.58	9.471%	$160.4626	$160.46	$160.45	$160.50
Purchase #5	$24.57	13.832%	$27.9685	$27.97	$27.95	$28.00
Purchase #6	$133.59	8.791%	$145.3339	$145.33	$145.35	$145.30
Purchase #7	$223.67	7.563%	$240.5862	$240.59	$240.60	$240.60
7 purchase totals =	$1,007.54		$1,105.3985	$1,105.41	$1,105.40	$1,105.40