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	$83.42	13.625%	$94.786	$94.79	$94.80	$94.80
Purchase #2	$91.52	3.619%	$94.8321	$94.83	$94.85	$94.80
Purchase #3	$82.81	4.656%	$86.6656	$86.67	$86.65	$86.70
Purchase #4	$12.77	12.653%	$14.3858	$14.39	$14.40	$14.40
Purchase #5	$168.37	4.240%	$175.5089	$175.51	$175.50	$175.50
Purchase #6	$120.48	8.851%	$131.1437	$131.14	$131.15	$131.10
Purchase #7	$153.76	4.430%	$160.5716	$160.57	$160.55	$160.60
7 purchase totals =	$713.13		$757.8937	$757.90	$757.90	$757.90