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	$216.70	5.787%	$229.2404	$229.24	$229.25	$229.20
Purchase #2	$71.25	4.249%	$74.2774	$74.28	$74.30	$74.30
Purchase #3	$232.85	10.320%	$256.8801	$256.88	$256.90	$256.90
Purchase #4	$234.26	13.138%	$265.0371	$265.04	$265.05	$265.00
Purchase #5	$33.43	13.239%	$37.8558	$37.86	$37.85	$37.90
Purchase #6	$78.37	5.743%	$82.8708	$82.87	$82.85	$82.90
Purchase #7	$52.69	4.607%	$55.1174	$55.12	$55.10	$55.10
7 purchase totals =	$919.55		$1,001.2790	$1,001.29	$1,001.30	$1,001.30