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	$201.32	11.478%	$224.4275	$224.43	$224.45	$224.40
Purchase #2	$54.70	4.743%	$57.2944	$57.29	$57.30	$57.30
Purchase #3	$50.54	12.494%	$56.8545	$56.85	$56.85	$56.90
Purchase #4	$196.57	9.865%	$215.9616	$215.96	$215.95	$216.00
Purchase #5	$59.91	6.455%	$63.7772	$63.78	$63.80	$63.80
Purchase #6	$79.43	12.792%	$89.5907	$89.59	$89.60	$89.60
Purchase #7	$17.34	13.216%	$19.6317	$19.63	$19.65	$19.60
7 purchase totals =	$659.81		$727.5376	$727.53	$727.60	$727.60