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	$43.58	4.592%	$45.5812	$45.58	$45.60	$45.60
Purchase #2	$7.55	3.315%	$7.8003	$7.80	$7.80	$7.80
Purchase #3	$227.50	3.815%	$236.1791	$236.18	$236.20	$236.20
Purchase #4	$133.86	4.485%	$139.8636	$139.86	$139.85	$139.90
Purchase #5	$131.71	9.192%	$143.8168	$143.82	$143.80	$143.80
Purchase #6	$133.62	7.580%	$143.7484	$143.75	$143.75	$143.70
Purchase #7	$187.52	13.302%	$212.4639	$212.46	$212.45	$212.50
7 purchase totals =	$865.34		$929.4533	$929.45	$929.45	$929.50