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	$61.63	9.614%	$67.5551	$67.56	$67.55	$67.60
Purchase #2	$118.90	11.740%	$132.8589	$132.86	$132.85	$132.90
Purchase #3	$66.36	9.429%	$72.6171	$72.62	$72.60	$72.60
Purchase #4	$198.39	10.600%	$219.4193	$219.42	$219.40	$219.40
Purchase #5	$159.53	4.361%	$166.4871	$166.49	$166.50	$166.50
Purchase #6	$116.36	8.857%	$126.666	$126.67	$126.65	$126.70
Purchase #7	$5.29	4.389%	$5.5222	$5.52	$5.50	$5.50
7 purchase totals =	$726.46		$791.1257	$791.14	$791.05	$791.20