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	$210.93	10.651%	$233.3962	$233.40	$233.40	$233.40
Purchase #2	$243.84	9.785%	$267.6997	$267.70	$267.70	$267.70
Purchase #3	$88.96	12.446%	$100.032	$100.03	$100.05	$100.00
Purchase #4	$192.95	11.642%	$215.4132	$215.41	$215.40	$215.40
Purchase #5	$86.82	5.211%	$91.3442	$91.34	$91.35	$91.30
Purchase #6	$10.53	8.247%	$11.3984	$11.40	$11.40	$11.40
Purchase #7	$168.48	5.240%	$177.3084	$177.31	$177.30	$177.30
7 purchase totals =	$1,002.51		$1,096.5921	$1,096.59	$1,096.60	$1,096.50