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	$33.89	9.656%	$37.1624	$37.16	$37.15	$37.20
Purchase #2	$245.96	4.314%	$256.5707	$256.57	$256.55	$256.60
Purchase #3	$8.38	8.473%	$9.09	$9.09	$9.10	$9.10
Purchase #4	$37.64	10.749%	$41.6859	$41.69	$41.70	$41.70
Purchase #5	$229.55	8.171%	$248.3065	$248.31	$248.30	$248.30
Purchase #6	$180.61	8.846%	$196.5868	$196.59	$196.60	$196.60
Purchase #7	$71.78	7.222%	$76.964	$76.96	$76.95	$77.00
7 purchase totals =	$807.81		$866.3663	$866.37	$866.35	$866.50