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	$75.28	13.698%	$85.5919	$85.59	$85.60	$85.60
Purchase #2	$55.87	7.520%	$60.0714	$60.07	$60.05	$60.10
Purchase #3	$99.41	8.625%	$107.9841	$107.98	$108.00	$108.00
Purchase #4	$185.50	3.805%	$192.5583	$192.56	$192.55	$192.60
Purchase #5	$183.68	9.372%	$200.8945	$200.89	$200.90	$200.90
Purchase #6	$235.57	10.205%	$259.6099	$259.61	$259.60	$259.60
Purchase #7	$199.79	10.533%	$220.8339	$220.83	$220.85	$220.80
7 purchase totals =	$1,035.10		$1,127.5440	$1,127.53	$1,127.55	$1,127.60