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	$101.83	4.618%	$106.5325	$106.53	$106.55	$106.50
Purchase #2	$179.39	7.238%	$192.3742	$192.37	$192.35	$192.40
Purchase #3	$162.87	5.825%	$172.3572	$172.36	$172.35	$172.40
Purchase #4	$83.88	9.684%	$92.0029	$92.00	$92.00	$92.00
Purchase #5	$238.56	7.192%	$255.7172	$255.72	$255.70	$255.70
Purchase #6	$176.38	8.769%	$191.8468	$191.85	$191.85	$191.80
Purchase #7	$205.60	8.384%	$222.8375	$222.84	$222.85	$222.80
7 purchase totals =	$1,148.51		$1,233.6683	$1,233.67	$1,233.65	$1,233.60