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	$184.50	13.426%	$209.271	$209.27	$209.25	$209.30
Purchase #2	$133.95	4.729%	$140.2845	$140.28	$140.30	$140.30
Purchase #3	$203.72	6.466%	$216.8925	$216.89	$216.90	$216.90
Purchase #4	$117.36	4.475%	$122.6119	$122.61	$122.60	$122.60
Purchase #5	$92.79	13.773%	$105.57	$105.57	$105.55	$105.60
Purchase #6	$59.86	11.513%	$66.7517	$66.75	$66.75	$66.80
Purchase #7	$64.55	13.801%	$73.4585	$73.46	$73.45	$73.50
7 purchase totals =	$856.73		$934.8401	$934.83	$934.80	$935.00