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	$206.97	13.321%	$234.5405	$234.54	$234.55	$234.50
Purchase #2	$61.73	4.215%	$64.3319	$64.33	$64.35	$64.30
Purchase #3	$111.35	6.163%	$118.2125	$118.21	$118.20	$118.20
Purchase #4	$17.90	12.530%	$20.1429	$20.14	$20.15	$20.10
Purchase #5	$179.88	6.813%	$192.1352	$192.14	$192.15	$192.10
Purchase #6	$144.78	4.528%	$151.3356	$151.34	$151.35	$151.30
Purchase #7	$218.33	4.331%	$227.7859	$227.79	$227.80	$227.80
7 purchase totals =	$940.94		$1,008.4845	$1,008.49	$1,008.55	$1,008.30