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	$211.79	11.380%	$235.8917	$235.89	$235.90	$235.90
Purchase #2	$81.56	11.643%	$91.056	$91.06	$91.05	$91.10
Purchase #3	$82.77	5.118%	$87.0062	$87.01	$87.00	$87.00
Purchase #4	$123.95	10.378%	$136.8135	$136.81	$136.80	$136.80
Purchase #5	$221.57	13.656%	$251.8276	$251.83	$251.85	$251.80
Purchase #6	$37.85	13.342%	$42.8999	$42.90	$42.90	$42.90
Purchase #7	$199.61	6.461%	$212.5068	$212.51	$212.50	$212.50
7 purchase totals =	$959.10		$1,058.0017	$1,058.01	$1,058.00	$1,058.00