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	$61.99	5.641%	$65.4869	$65.49	$65.50	$65.50
Purchase #2	$45.33	4.447%	$47.3458	$47.35	$47.35	$47.30
Purchase #3	$102.76	3.787%	$106.6515	$106.65	$106.65	$106.70
Purchase #4	$7.97	6.776%	$8.51	$8.51	$8.50	$8.50
Purchase #5	$107.86	6.279%	$114.6325	$114.63	$114.65	$114.60
Purchase #6	$40.59	3.210%	$41.8929	$41.89	$41.90	$41.90
Purchase #7	$214.89	3.503%	$222.4176	$222.42	$222.40	$222.40
7 purchase totals =	$581.39		$606.9372	$606.94	$606.95	$606.90