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	$97.55	5.703%	$103.1133	$103.11	$103.10	$103.10
Purchase #2	$210.41	5.247%	$221.4502	$221.45	$221.45	$221.50
Purchase #3	$18.73	12.598%	$21.0896	$21.09	$21.10	$21.10
Purchase #4	$227.54	11.788%	$254.3624	$254.36	$254.35	$254.40
Purchase #5	$158.86	4.447%	$165.9245	$165.92	$165.90	$165.90
Purchase #6	$93.96	12.448%	$105.6561	$105.66	$105.65	$105.70
Purchase #7	$121.41	13.647%	$137.9788	$137.98	$138.00	$138.00
7 purchase totals =	$928.46		$1,009.5749	$1,009.57	$1,009.55	$1,009.70