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	$94.92	7.396%	$101.9403	$101.94	$101.95	$101.90
Purchase #2	$242.87	5.342%	$255.8441	$255.84	$255.85	$255.80
Purchase #3	$177.62	10.372%	$196.0427	$196.04	$196.05	$196.00
Purchase #4	$207.40	7.265%	$222.4676	$222.47	$222.45	$222.50
Purchase #5	$27.81	12.496%	$31.2851	$31.29	$31.30	$31.30
Purchase #6	$172.78	9.818%	$189.7435	$189.74	$189.75	$189.70
Purchase #7	$11.54	9.409%	$12.6258	$12.63	$12.65	$12.60
7 purchase totals =	$934.94		$1,009.9491	$1,009.95	$1,010.00	$1,009.80