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	$189.82	5.129%	$199.5559	$199.56	$199.55	$199.60
Purchase #2	$135.78	11.541%	$151.4504	$151.45	$151.45	$151.50
Purchase #3	$175.78	5.537%	$185.5129	$185.51	$185.50	$185.50
Purchase #4	$191.42	12.606%	$215.5504	$215.55	$215.55	$215.60
Purchase #5	$188.85	5.709%	$199.6314	$199.63	$199.65	$199.60
Purchase #6	$194.54	3.189%	$200.7439	$200.74	$200.75	$200.70
Purchase #7	$85.88	6.488%	$91.4519	$91.45	$91.45	$91.50
7 purchase totals =	$1,162.07		$1,243.8968	$1,243.89	$1,243.90	$1,244.00