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	$238.38	3.571%	$246.8925	$246.89	$246.90	$246.90
Purchase #2	$20.43	3.586%	$21.1626	$21.16	$21.15	$21.20
Purchase #3	$162.69	10.406%	$179.6195	$179.62	$179.60	$179.60
Purchase #4	$197.54	11.326%	$219.9134	$219.91	$219.90	$219.90
Purchase #5	$96.62	4.326%	$100.7998	$100.80	$100.80	$100.80
Purchase #6	$134.56	7.515%	$144.6722	$144.67	$144.65	$144.70
Purchase #7	$65.49	10.236%	$72.1936	$72.19	$72.20	$72.20
7 purchase totals =	$915.71		$985.2536	$985.24	$985.20	$985.30