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	$183.81	4.639%	$192.3369	$192.34	$192.35	$192.30
Purchase #2	$79.92	10.173%	$88.0503	$88.05	$88.05	$88.10
Purchase #3	$144.33	13.794%	$164.2389	$164.24	$164.25	$164.20
Purchase #4	$229.28	10.662%	$253.7258	$253.73	$253.75	$253.70
Purchase #5	$217.94	4.562%	$227.8824	$227.88	$227.90	$227.90
Purchase #6	$12.78	6.358%	$13.5926	$13.59	$13.60	$13.60
Purchase #7	$80.83	12.856%	$91.2215	$91.22	$91.20	$91.20
7 purchase totals =	$948.89		$1,031.0484	$1,031.05	$1,031.10	$1,031.00