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	$229.69	11.816%	$256.8302	$256.83	$256.85	$256.80
Purchase #2	$42.39	8.845%	$46.1394	$46.14	$46.15	$46.10
Purchase #3	$201.25	10.777%	$222.9387	$222.94	$222.95	$222.90
Purchase #4	$249.38	10.830%	$276.3879	$276.39	$276.40	$276.40
Purchase #5	$208.41	8.849%	$226.8522	$226.85	$226.85	$226.90
Purchase #6	$144.43	5.598%	$152.5152	$152.52	$152.50	$152.50
Purchase #7	$238.81	11.304%	$265.8051	$265.81	$265.80	$265.80
7 purchase totals =	$1,314.36		$1,447.4687	$1,447.48	$1,447.50	$1,447.40