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	$46.33	5.729%	$48.9842	$48.98	$49.00	$49.00
Purchase #2	$141.67	11.694%	$158.2369	$158.24	$158.25	$158.20
Purchase #3	$75.85	3.439%	$78.4585	$78.46	$78.45	$78.50
Purchase #4	$198.79	8.134%	$214.9596	$214.96	$214.95	$215.00
Purchase #5	$223.75	8.317%	$242.3593	$242.36	$242.35	$242.40
Purchase #6	$137.73	4.283%	$143.629	$143.63	$143.65	$143.60
Purchase #7	$81.25	10.701%	$89.9446	$89.94	$89.95	$89.90
7 purchase totals =	$905.37		$976.5721	$976.57	$976.60	$976.60