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	$83.34	7.221%	$89.358	$89.36	$89.35	$89.40
Purchase #2	$51.61	10.651%	$57.107	$57.11	$57.10	$57.10
Purchase #3	$75.98	12.527%	$85.498	$85.50	$85.50	$85.50
Purchase #4	$74.90	4.424%	$78.2136	$78.21	$78.20	$78.20
Purchase #5	$111.67	4.680%	$116.8962	$116.90	$116.90	$116.90
Purchase #6	$104.44	12.693%	$117.6966	$117.70	$117.70	$117.70
Purchase #7	$236.48	5.393%	$249.2334	$249.23	$249.25	$249.20
7 purchase totals =	$738.42		$794.0028	$794.01	$794.00	$794.00