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	$94.86	11.513%	$105.7812	$105.78	$105.80	$105.80
Purchase #2	$57.67	3.430%	$59.6481	$59.65	$59.65	$59.60
Purchase #3	$172.86	8.687%	$187.8763	$187.88	$187.90	$187.90
Purchase #4	$202.28	9.310%	$221.1123	$221.11	$221.10	$221.10
Purchase #5	$33.47	9.414%	$36.6209	$36.62	$36.60	$36.60
Purchase #6	$25.68	8.843%	$27.9509	$27.95	$27.95	$28.00
Purchase #7	$44.95	3.428%	$46.4909	$46.49	$46.50	$46.50
7 purchase totals =	$631.77		$685.4806	$685.48	$685.50	$685.50