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	$28.66	13.326%	$32.4792	$32.48	$32.50	$32.50
Purchase #2	$244.66	4.435%	$255.5107	$255.51	$255.50	$255.50
Purchase #3	$35.43	6.628%	$37.7783	$37.78	$37.80	$37.80
Purchase #4	$150.53	12.863%	$169.8927	$169.89	$169.90	$169.90
Purchase #5	$19.44	4.767%	$20.3667	$20.37	$20.35	$20.40
Purchase #6	$206.81	8.573%	$224.5398	$224.54	$224.55	$224.50
Purchase #7	$187.73	9.231%	$205.0594	$205.06	$205.05	$205.10
7 purchase totals =	$873.26		$945.6268	$945.63	$945.65	$945.70