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	$98.85	6.197%	$104.9757	$104.98	$105.00	$105.00
Purchase #2	$152.48	3.243%	$157.4249	$157.42	$157.40	$157.40
Purchase #3	$53.72	6.614%	$57.273	$57.27	$57.25	$57.30
Purchase #4	$42.87	12.774%	$48.3462	$48.35	$48.35	$48.30
Purchase #5	$18.89	3.324%	$19.5179	$19.52	$19.50	$19.50
Purchase #6	$65.96	8.826%	$71.7816	$71.78	$71.80	$71.80
Purchase #7	$144.25	5.157%	$151.689	$151.69	$151.70	$151.70
7 purchase totals =	$577.02		$611.0083	$611.01	$611.00	$611.00