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	$116.42	4.542%	$121.7078	$121.71	$121.70	$121.70
Purchase #2	$96.55	3.668%	$100.0915	$100.09	$100.10	$100.10
Purchase #3	$111.53	12.489%	$125.459	$125.46	$125.45	$125.50
Purchase #4	$225.82	3.221%	$233.0937	$233.09	$233.10	$233.10
Purchase #5	$242.88	13.454%	$275.5571	$275.56	$275.55	$275.60
Purchase #6	$248.55	5.625%	$262.5309	$262.53	$262.55	$262.50
Purchase #7	$92.81	8.639%	$100.8279	$100.83	$100.85	$100.80
7 purchase totals =	$1,134.56		$1,219.2679	$1,219.27	$1,219.30	$1,219.30