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	$32.41	3.281%	$33.4734	$33.47	$33.45	$33.50
Purchase #2	$199.86	8.245%	$216.3385	$216.34	$216.35	$216.30
Purchase #3	$209.52	8.270%	$226.8473	$226.85	$226.85	$226.80
Purchase #4	$214.36	12.872%	$241.9524	$241.95	$241.95	$242.00
Purchase #5	$160.29	7.861%	$172.8904	$172.89	$172.90	$172.90
Purchase #6	$40.73	12.610%	$45.8661	$45.87	$45.85	$45.90
Purchase #7	$197.52	4.352%	$206.1161	$206.12	$206.10	$206.10
7 purchase totals =	$1,054.69		$1,143.4842	$1,143.49	$1,143.45	$1,143.50