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	$107.56	4.245%	$112.1259	$112.13	$112.15	$112.10
Purchase #2	$151.52	3.196%	$156.3626	$156.36	$156.35	$156.40
Purchase #3	$114.97	8.467%	$124.7045	$124.70	$124.70	$124.70
Purchase #4	$99.39	3.198%	$102.5685	$102.57	$102.55	$102.60
Purchase #5	$95.95	7.268%	$102.9236	$102.92	$102.90	$102.90
Purchase #6	$53.89	5.586%	$56.9003	$56.90	$56.90	$56.90
Purchase #7	$52.25	13.774%	$59.4469	$59.45	$59.45	$59.40
7 purchase totals =	$675.53		$715.0323	$715.03	$715.00	$715.00