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	$135.27	12.220%	$151.8	$151.80	$151.80	$151.80
Purchase #2	$241.47	11.280%	$268.7078	$268.71	$268.70	$268.70
Purchase #3	$29.66	10.277%	$32.7082	$32.71	$32.70	$32.70
Purchase #4	$68.49	5.151%	$72.0179	$72.02	$72.00	$72.00
Purchase #5	$152.76	7.640%	$164.4309	$164.43	$164.45	$164.40
Purchase #6	$187.35	9.206%	$204.5974	$204.60	$204.60	$204.60
Purchase #7	$227.72	12.832%	$256.941	$256.94	$256.95	$256.90
7 purchase totals =	$1,042.72		$1,151.2032	$1,151.21	$1,151.20	$1,151.10