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	$124.84	8.483%	$135.4302	$135.43	$135.45	$135.40
Purchase #2	$95.98	4.573%	$100.3692	$100.37	$100.35	$100.40
Purchase #3	$35.96	5.320%	$37.8731	$37.87	$37.85	$37.90
Purchase #4	$156.38	6.175%	$166.0365	$166.04	$166.05	$166.00
Purchase #5	$110.61	8.377%	$119.8758	$119.88	$119.90	$119.90
Purchase #6	$155.75	10.539%	$172.1645	$172.16	$172.15	$172.20
Purchase #7	$218.72	5.230%	$230.1591	$230.16	$230.15	$230.20
7 purchase totals =	$898.24		$961.9084	$961.91	$961.90	$962.00