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	$87.55	3.500%	$90.6143	$90.61	$90.60	$90.60
Purchase #2	$35.96	12.653%	$40.51	$40.51	$40.50	$40.50
Purchase #3	$45.73	5.222%	$48.118	$48.12	$48.10	$48.10
Purchase #4	$53.78	7.843%	$57.998	$58.00	$58.00	$58.00
Purchase #5	$76.51	9.873%	$84.0638	$84.06	$84.05	$84.10
Purchase #6	$206.49	7.849%	$222.6974	$222.70	$222.70	$222.70
Purchase #7	$209.80	13.582%	$238.295	$238.30	$238.30	$238.30
7 purchase totals =	$715.82		$782.2965	$782.30	$782.25	$782.30