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	$165.64	12.651%	$186.5951	$186.60	$186.60	$186.60
Purchase #2	$66.29	8.540%	$71.9512	$71.95	$71.95	$72.00
Purchase #3	$128.71	12.308%	$144.5516	$144.55	$144.55	$144.60
Purchase #4	$191.55	5.754%	$202.5718	$202.57	$202.55	$202.60
Purchase #5	$242.61	8.160%	$262.407	$262.41	$262.40	$262.40
Purchase #6	$39.51	3.188%	$40.7696	$40.77	$40.75	$40.80
Purchase #7	$221.88	7.686%	$238.9337	$238.93	$238.95	$238.90
7 purchase totals =	$1,056.19		$1,147.7800	$1,147.78	$1,147.75	$1,147.90