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	$180.79	8.197%	$195.6094	$195.61	$195.60	$195.60
Purchase #2	$239.50	6.540%	$255.1633	$255.16	$255.15	$255.20
Purchase #3	$40.27	13.232%	$45.5985	$45.60	$45.60	$45.60
Purchase #4	$86.74	13.122%	$98.122	$98.12	$98.10	$98.10
Purchase #5	$75.99	9.850%	$83.475	$83.48	$83.50	$83.50
Purchase #6	$100.64	8.347%	$109.0404	$109.04	$109.05	$109.00
Purchase #7	$151.59	13.284%	$171.7272	$171.73	$171.75	$171.70
7 purchase totals =	$875.52		$958.7358	$958.74	$958.75	$958.70