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	$221.67	10.692%	$245.371	$245.37	$245.35	$245.40
Purchase #2	$126.60	4.507%	$132.3059	$132.31	$132.30	$132.30
Purchase #3	$240.43	10.165%	$264.8697	$264.87	$264.85	$264.90
Purchase #4	$20.71	5.218%	$21.7906	$21.79	$21.80	$21.80
Purchase #5	$90.50	11.554%	$100.9564	$100.96	$100.95	$101.00
Purchase #6	$223.44	9.172%	$243.9339	$243.93	$243.95	$243.90
Purchase #7	$55.34	12.532%	$62.2752	$62.28	$62.30	$62.30
7 purchase totals =	$978.69		$1,071.5027	$1,071.51	$1,071.50	$1,071.60