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	$93.55	5.254%	$98.4651	$98.47	$98.45	$98.50
Purchase #2	$201.83	8.341%	$218.6646	$218.66	$218.65	$218.70
Purchase #3	$111.31	12.829%	$125.59	$125.59	$125.60	$125.60
Purchase #4	$125.77	9.334%	$137.5094	$137.51	$137.50	$137.50
Purchase #5	$223.81	8.474%	$242.7757	$242.78	$242.80	$242.80
Purchase #6	$65.49	6.601%	$69.813	$69.81	$69.80	$69.80
Purchase #7	$100.76	11.298%	$112.1439	$112.14	$112.15	$112.10
7 purchase totals =	$922.52		$1,004.9617	$1,004.96	$1,004.95	$1,005.00