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	$139.89	7.774%	$150.765	$150.77	$150.75	$150.80
Purchase #2	$194.57	10.410%	$214.8247	$214.82	$214.80	$214.80
Purchase #3	$40.81	8.214%	$44.1621	$44.16	$44.15	$44.20
Purchase #4	$212.59	5.213%	$223.6723	$223.67	$223.65	$223.70
Purchase #5	$226.67	5.560%	$239.2729	$239.27	$239.25	$239.30
Purchase #6	$64.78	10.429%	$71.5359	$71.54	$71.55	$71.50
Purchase #7	$136.42	13.872%	$155.3442	$155.34	$155.35	$155.30
7 purchase totals =	$1,015.73		$1,099.5771	$1,099.57	$1,099.50	$1,099.60