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	$219.51	9.256%	$239.8278	$239.83	$239.85	$239.80
Purchase #2	$235.59	7.647%	$253.6056	$253.61	$253.60	$253.60
Purchase #3	$141.52	9.452%	$154.8965	$154.90	$154.90	$154.90
Purchase #4	$104.73	8.747%	$113.8907	$113.89	$113.90	$113.90
Purchase #5	$46.33	11.850%	$51.8201	$51.82	$51.80	$51.80
Purchase #6	$216.68	3.228%	$223.6744	$223.67	$223.65	$223.70
Purchase #7	$188.55	6.428%	$200.67	$200.67	$200.65	$200.70
7 purchase totals =	$1,152.91		$1,238.3851	$1,238.39	$1,238.35	$1,238.40