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	$202.59	5.121%	$212.9646	$212.96	$212.95	$213.00
Purchase #2	$160.43	7.767%	$172.8906	$172.89	$172.90	$172.90
Purchase #3	$136.46	4.646%	$142.7999	$142.80	$142.80	$142.80
Purchase #4	$100.47	13.315%	$113.8476	$113.85	$113.85	$113.80
Purchase #5	$239.43	5.763%	$253.2284	$253.23	$253.25	$253.20
Purchase #6	$100.41	8.327%	$108.7711	$108.77	$108.75	$108.80
Purchase #7	$192.97	13.178%	$218.3996	$218.40	$218.40	$218.40
7 purchase totals =	$1,132.76		$1,222.9018	$1,222.90	$1,222.90	$1,222.90