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	$139.28	12.628%	$156.8683	$156.87	$156.85	$156.90
Purchase #2	$91.86	4.756%	$96.2289	$96.23	$96.25	$96.20
Purchase #3	$209.85	10.321%	$231.5086	$231.51	$231.50	$231.50
Purchase #4	$104.47	8.629%	$113.4847	$113.48	$113.50	$113.50
Purchase #5	$76.96	10.850%	$85.3102	$85.31	$85.30	$85.30
Purchase #6	$108.56	7.375%	$116.5663	$116.57	$116.55	$116.60
Purchase #7	$232.91	4.490%	$243.3677	$243.37	$243.35	$243.40
7 purchase totals =	$963.89		$1,043.3347	$1,043.34	$1,043.30	$1,043.40