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	$203.60	12.757%	$229.5733	$229.57	$229.55	$229.60
Purchase #2	$196.46	13.511%	$223.0037	$223.00	$223.00	$223.00
Purchase #3	$36.26	8.313%	$39.2743	$39.27	$39.25	$39.30
Purchase #4	$91.44	12.259%	$102.6496	$102.65	$102.65	$102.60
Purchase #5	$82.57	8.763%	$89.8056	$89.81	$89.80	$89.80
Purchase #6	$186.80	4.192%	$194.6307	$194.63	$194.65	$194.60
Purchase #7	$35.50	5.456%	$37.4369	$37.44	$37.45	$37.40
7 purchase totals =	$832.63		$916.3741	$916.37	$916.35	$916.30