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	$177.90	9.432%	$194.6795	$194.68	$194.70	$194.70
Purchase #2	$238.57	10.586%	$263.825	$263.83	$263.85	$263.80
Purchase #3	$50.47	4.845%	$52.9153	$52.92	$52.90	$52.90
Purchase #4	$84.78	9.266%	$92.6357	$92.64	$92.65	$92.60
Purchase #5	$86.29	3.264%	$89.1065	$89.11	$89.10	$89.10
Purchase #6	$29.82	10.354%	$32.9076	$32.91	$32.90	$32.90
Purchase #7	$201.96	13.624%	$229.475	$229.48	$229.50	$229.50
7 purchase totals =	$869.79		$955.5446	$955.57	$955.60	$955.50