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	$97.39	8.523%	$105.6905	$105.69	$105.70	$105.70
Purchase #2	$11.52	11.308%	$12.8227	$12.82	$12.80	$12.80
Purchase #3	$93.44	13.345%	$105.9096	$105.91	$105.90	$105.90
Purchase #4	$28.91	12.474%	$32.5162	$32.52	$32.50	$32.50
Purchase #5	$112.81	11.123%	$125.3579	$125.36	$125.35	$125.40
Purchase #6	$28.25	13.305%	$32.0087	$32.01	$32.00	$32.00
Purchase #7	$22.71	9.766%	$24.9279	$24.93	$24.95	$24.90
7 purchase totals =	$395.03		$439.2335	$439.24	$439.20	$439.20