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	$242.30	5.172%	$254.8318	$254.83	$254.85	$254.80
Purchase #2	$27.38	3.266%	$28.2742	$28.27	$28.25	$28.30
Purchase #3	$169.32	6.625%	$180.5375	$180.54	$180.55	$180.50
Purchase #4	$217.72	12.854%	$245.7057	$245.71	$245.70	$245.70
Purchase #5	$114.48	3.114%	$118.0449	$118.04	$118.05	$118.00
Purchase #6	$126.32	8.113%	$136.5683	$136.57	$136.55	$136.60
Purchase #7	$148.57	7.461%	$159.6548	$159.65	$159.65	$159.70
7 purchase totals =	$1,046.09		$1,123.6172	$1,123.61	$1,123.60	$1,123.60