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	$137.81	4.727%	$144.3243	$144.32	$144.30	$144.30
Purchase #2	$159.80	5.402%	$168.4324	$168.43	$168.45	$168.40
Purchase #3	$239.94	11.761%	$268.1593	$268.16	$268.15	$268.20
Purchase #4	$164.41	6.545%	$175.1706	$175.17	$175.15	$175.20
Purchase #5	$48.48	13.651%	$55.098	$55.10	$55.10	$55.10
Purchase #6	$113.80	5.375%	$119.9168	$119.92	$119.90	$119.90
Purchase #7	$116.91	13.268%	$132.4216	$132.42	$132.40	$132.40
7 purchase totals =	$981.15		$1,063.5230	$1,063.52	$1,063.45	$1,063.50