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	$72.63	7.420%	$78.0191	$78.02	$78.00	$78.00
Purchase #2	$155.28	4.700%	$162.5782	$162.58	$162.60	$162.60
Purchase #3	$212.92	13.543%	$241.7558	$241.76	$241.75	$241.80
Purchase #4	$43.28	9.459%	$47.3739	$47.37	$47.35	$47.40
Purchase #5	$150.32	5.198%	$158.1336	$158.13	$158.15	$158.10
Purchase #6	$142.73	11.756%	$159.5093	$159.51	$159.50	$159.50
Purchase #7	$153.84	6.270%	$163.4858	$163.49	$163.50	$163.50
7 purchase totals =	$931.00		$1,010.8557	$1,010.86	$1,010.85	$1,010.90