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	$61.96	4.728%	$64.8895	$64.89	$64.90	$64.90
Purchase #2	$170.72	11.722%	$190.7318	$190.73	$190.75	$190.70
Purchase #3	$92.44	11.449%	$103.0235	$103.02	$103.00	$103.00
Purchase #4	$167.89	8.818%	$182.6945	$182.69	$182.70	$182.70
Purchase #5	$219.72	8.579%	$238.5698	$238.57	$238.55	$238.60
Purchase #6	$85.95	11.559%	$95.885	$95.89	$95.90	$95.90
Purchase #7	$62.55	12.850%	$70.5877	$70.59	$70.60	$70.60
7 purchase totals =	$861.23		$946.3818	$946.38	$946.40	$946.40