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	$83.98	5.325%	$88.4519	$88.45	$88.45	$88.50
Purchase #2	$29.35	10.732%	$32.4998	$32.50	$32.50	$32.50
Purchase #3	$235.28	12.162%	$263.8948	$263.89	$263.90	$263.90
Purchase #4	$245.44	4.218%	$255.7927	$255.79	$255.80	$255.80
Purchase #5	$146.60	6.384%	$155.9589	$155.96	$155.95	$156.00
Purchase #6	$43.48	11.772%	$48.5985	$48.60	$48.60	$48.60
Purchase #7	$122.66	8.368%	$132.9242	$132.92	$132.90	$132.90
7 purchase totals =	$906.79		$978.1208	$978.11	$978.10	$978.20