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	$105.98	12.145%	$118.8513	$118.85	$118.85	$118.90
Purchase #2	$62.46	3.511%	$64.653	$64.65	$64.65	$64.70
Purchase #3	$190.64	3.192%	$196.7252	$196.73	$196.75	$196.70
Purchase #4	$141.84	7.591%	$152.6071	$152.61	$152.60	$152.60
Purchase #5	$117.77	13.238%	$133.3604	$133.36	$133.35	$133.40
Purchase #6	$197.65	6.162%	$209.8292	$209.83	$209.85	$209.80
Purchase #7	$29.93	9.441%	$32.7557	$32.76	$32.75	$32.80
7 purchase totals =	$846.27		$908.7819	$908.79	$908.80	$908.90