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	$109.41	5.806%	$115.7623	$115.76	$115.75	$115.80
Purchase #2	$52.69	12.705%	$59.3843	$59.38	$59.40	$59.40
Purchase #3	$14.67	5.279%	$15.4444	$15.44	$15.45	$15.40
Purchase #4	$186.52	5.469%	$196.7208	$196.72	$196.70	$196.70
Purchase #5	$160.65	12.601%	$180.8935	$180.89	$180.90	$180.90
Purchase #6	$185.81	11.401%	$206.9942	$206.99	$207.00	$207.00
Purchase #7	$132.62	8.739%	$144.2097	$144.21	$144.20	$144.20
7 purchase totals =	$842.37		$919.4092	$919.39	$919.40	$919.40