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	$151.29	11.441%	$168.5991	$168.60	$168.60	$168.60
Purchase #2	$223.72	13.310%	$253.4971	$253.50	$253.50	$253.50
Purchase #3	$214.72	7.693%	$231.2384	$231.24	$231.25	$231.20
Purchase #4	$101.77	7.484%	$109.3865	$109.39	$109.40	$109.40
Purchase #5	$36.38	6.292%	$38.669	$38.67	$38.65	$38.70
Purchase #6	$71.74	10.328%	$79.1493	$79.15	$79.15	$79.10
Purchase #7	$85.49	10.722%	$94.6562	$94.66	$94.65	$94.70
7 purchase totals =	$885.11		$975.1956	$975.21	$975.20	$975.20