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	$54.37	5.759%	$57.5012	$57.50	$57.50	$57.50
Purchase #2	$43.26	11.134%	$48.0766	$48.08	$48.10	$48.10
Purchase #3	$98.63	6.427%	$104.969	$104.97	$104.95	$105.00
Purchase #4	$249.83	6.277%	$265.5118	$265.51	$265.50	$265.50
Purchase #5	$209.53	9.472%	$229.3767	$229.38	$229.40	$229.40
Purchase #6	$217.94	3.651%	$225.897	$225.90	$225.90	$225.90
Purchase #7	$115.85	12.513%	$130.3463	$130.35	$130.35	$130.30
7 purchase totals =	$989.41		$1,061.6786	$1,061.69	$1,061.70	$1,061.70