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	$43.40	6.134%	$46.0622	$46.06	$46.05	$46.10
Purchase #2	$85.63	11.706%	$95.6538	$95.65	$95.65	$95.70
Purchase #3	$83.77	6.818%	$89.4814	$89.48	$89.50	$89.50
Purchase #4	$70.29	11.746%	$78.5463	$78.55	$78.55	$78.50
Purchase #5	$241.62	13.439%	$274.0913	$274.09	$274.10	$274.10
Purchase #6	$181.26	12.269%	$203.4988	$203.50	$203.50	$203.50
Purchase #7	$114.40	7.817%	$123.3426	$123.34	$123.35	$123.30
7 purchase totals =	$820.37		$910.6764	$910.67	$910.70	$910.70