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	$131.45	8.467%	$142.5799	$142.58	$142.60	$142.60
Purchase #2	$141.32	4.120%	$147.1424	$147.14	$147.15	$147.10
Purchase #3	$53.74	11.331%	$59.8293	$59.83	$59.85	$59.80
Purchase #4	$20.65	7.438%	$22.1859	$22.19	$22.20	$22.20
Purchase #5	$223.58	11.635%	$249.5935	$249.59	$249.60	$249.60
Purchase #6	$102.95	5.767%	$108.8871	$108.89	$108.90	$108.90
Purchase #7	$211.96	7.524%	$227.9079	$227.91	$227.90	$227.90
7 purchase totals =	$885.65		$958.1260	$958.13	$958.20	$958.10