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	$133.94	3.414%	$138.5127	$138.51	$138.50	$138.50
Purchase #2	$75.59	7.813%	$81.4958	$81.50	$81.50	$81.50
Purchase #3	$96.76	13.195%	$109.5275	$109.53	$109.55	$109.50
Purchase #4	$248.59	7.358%	$266.8813	$266.88	$266.90	$266.90
Purchase #5	$99.48	11.186%	$110.6078	$110.61	$110.60	$110.60
Purchase #6	$104.59	6.368%	$111.2503	$111.25	$111.25	$111.30
Purchase #7	$216.70	4.866%	$227.2446	$227.24	$227.25	$227.20
7 purchase totals =	$975.65		$1,045.5200	$1,045.52	$1,045.55	$1,045.50