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	$18.73	4.687%	$19.6079	$19.61	$19.60	$19.60
Purchase #2	$162.27	13.667%	$184.4474	$184.45	$184.45	$184.40
Purchase #3	$131.74	11.673%	$147.118	$147.12	$147.10	$147.10
Purchase #4	$178.54	11.456%	$198.9935	$198.99	$199.00	$199.00
Purchase #5	$118.48	4.485%	$123.7938	$123.79	$123.80	$123.80
Purchase #6	$214.74	12.642%	$241.8874	$241.89	$241.90	$241.90
Purchase #7	$82.27	12.624%	$92.6558	$92.66	$92.65	$92.70
7 purchase totals =	$906.77		$1,008.5038	$1,008.51	$1,008.50	$1,008.50