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	$230.78	5.164%	$242.6975	$242.70	$242.70	$242.70
Purchase #2	$53.27	12.391%	$59.8707	$59.87	$59.85	$59.90
Purchase #3	$63.43	3.356%	$65.5587	$65.56	$65.55	$65.60
Purchase #4	$56.37	5.362%	$59.3926	$59.39	$59.40	$59.40
Purchase #5	$215.35	3.720%	$223.361	$223.36	$223.35	$223.40
Purchase #6	$172.50	13.457%	$195.7133	$195.71	$195.70	$195.70
Purchase #7	$143.66	4.262%	$149.7828	$149.78	$149.80	$149.80
7 purchase totals =	$935.36		$996.3766	$996.37	$996.35	$996.50