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	$77.37	11.658%	$86.3898	$86.39	$86.40	$86.40
Purchase #2	$61.56	11.511%	$68.6462	$68.65	$68.65	$68.60
Purchase #3	$150.92	8.869%	$164.3051	$164.31	$164.30	$164.30
Purchase #4	$131.81	6.610%	$140.5226	$140.52	$140.50	$140.50
Purchase #5	$185.46	8.318%	$200.8866	$200.89	$200.90	$200.90
Purchase #6	$112.80	10.350%	$124.4748	$124.47	$124.45	$124.50
Purchase #7	$33.83	11.155%	$37.6037	$37.60	$37.60	$37.60
7 purchase totals =	$753.75		$822.8288	$822.83	$822.80	$822.80