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	$240.97	5.303%	$253.7486	$253.75	$253.75	$253.70
Purchase #2	$50.71	8.263%	$54.9002	$54.90	$54.90	$54.90
Purchase #3	$132.81	6.465%	$141.3962	$141.40	$141.40	$141.40
Purchase #4	$12.88	5.375%	$13.5723	$13.57	$13.55	$13.60
Purchase #5	$150.74	11.781%	$168.4987	$168.50	$168.50	$168.50
Purchase #6	$93.78	7.730%	$101.0292	$101.03	$101.05	$101.00
Purchase #7	$178.85	9.668%	$196.1412	$196.14	$196.15	$196.10
7 purchase totals =	$860.74		$929.2864	$929.29	$929.30	$929.20