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	$38.83	8.569%	$42.1573	$42.16	$42.15	$42.20
Purchase #2	$138.91	8.648%	$150.9229	$150.92	$150.90	$150.90
Purchase #3	$227.27	6.275%	$241.5312	$241.53	$241.55	$241.50
Purchase #4	$153.50	7.459%	$164.9496	$164.95	$164.95	$164.90
Purchase #5	$220.69	4.194%	$229.9457	$229.95	$229.95	$229.90
Purchase #6	$107.41	11.664%	$119.9383	$119.94	$119.95	$119.90
Purchase #7	$141.28	3.198%	$145.7981	$145.80	$145.80	$145.80
7 purchase totals =	$1,027.89		$1,095.2431	$1,095.25	$1,095.25	$1,095.10