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	$153.33	6.334%	$163.0419	$163.04	$163.05	$163.00
Purchase #2	$111.98	11.860%	$125.2608	$125.26	$125.25	$125.30
Purchase #3	$104.75	12.155%	$117.4824	$117.48	$117.50	$117.50
Purchase #4	$71.96	8.722%	$78.2364	$78.24	$78.25	$78.20
Purchase #5	$172.77	10.682%	$191.2253	$191.23	$191.25	$191.20
Purchase #6	$120.89	5.260%	$127.2488	$127.25	$127.25	$127.20
Purchase #7	$147.64	4.547%	$154.3532	$154.35	$154.35	$154.40
7 purchase totals =	$883.32		$956.8488	$956.85	$956.90	$956.80