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	$86.87	3.628%	$90.0216	$90.02	$90.00	$90.00
Purchase #2	$5.96	4.561%	$6.2318	$6.23	$6.25	$6.20
Purchase #3	$155.55	3.480%	$160.9631	$160.96	$160.95	$161.00
Purchase #4	$133.79	5.873%	$141.6475	$141.65	$141.65	$141.60
Purchase #5	$48.39	10.811%	$53.6214	$53.62	$53.60	$53.60
Purchase #6	$74.32	11.327%	$82.7382	$82.74	$82.75	$82.70
Purchase #7	$172.72	10.314%	$190.5343	$190.53	$190.55	$190.50
7 purchase totals =	$677.60		$725.7579	$725.75	$725.75	$725.60