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	$41.69	4.362%	$43.5085	$43.51	$43.50	$43.50
Purchase #2	$77.71	11.117%	$86.349	$86.35	$86.35	$86.30
Purchase #3	$91.99	8.167%	$99.5028	$99.50	$99.50	$99.50
Purchase #4	$146.35	13.578%	$166.2214	$166.22	$166.20	$166.20
Purchase #5	$161.94	11.298%	$180.236	$180.24	$180.25	$180.20
Purchase #6	$78.42	6.631%	$83.62	$83.62	$83.60	$83.60
Purchase #7	$206.40	6.579%	$219.9791	$219.98	$220.00	$220.00
7 purchase totals =	$804.50		$879.4168	$879.42	$879.40	$879.30