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	$40.95	6.116%	$43.4545	$43.45	$43.45	$43.50
Purchase #2	$136.50	11.234%	$151.8344	$151.83	$151.85	$151.80
Purchase #3	$193.86	7.609%	$208.6108	$208.61	$208.60	$208.60
Purchase #4	$36.64	9.295%	$40.0457	$40.05	$40.05	$40.00
Purchase #5	$48.86	5.118%	$51.3607	$51.36	$51.35	$51.40
Purchase #6	$250.55	8.842%	$272.7036	$272.70	$272.70	$272.70
Purchase #7	$240.53	12.386%	$270.322	$270.32	$270.30	$270.30
7 purchase totals =	$947.89		$1,038.3317	$1,038.32	$1,038.30	$1,038.30