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	$32.76	9.731%	$35.9479	$35.95	$35.95	$35.90
Purchase #2	$79.27	7.724%	$85.3928	$85.39	$85.40	$85.40
Purchase #3	$224.70	10.102%	$247.3992	$247.40	$247.40	$247.40
Purchase #4	$131.30	8.162%	$142.0167	$142.02	$142.00	$142.00
Purchase #5	$112.87	13.752%	$128.3919	$128.39	$128.40	$128.40
Purchase #6	$120.35	13.844%	$137.0113	$137.01	$137.00	$137.00
Purchase #7	$43.73	7.168%	$46.8646	$46.86	$46.85	$46.90
7 purchase totals =	$744.98		$823.0244	$823.02	$823.00	$823.00