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	$237.30	5.459%	$250.2542	$250.25	$250.25	$250.30
Purchase #2	$73.69	6.301%	$78.3332	$78.33	$78.35	$78.30
Purchase #3	$70.25	8.763%	$76.406	$76.41	$76.40	$76.40
Purchase #4	$46.91	8.471%	$50.8837	$50.88	$50.90	$50.90
Purchase #5	$86.90	5.315%	$91.5187	$91.52	$91.50	$91.50
Purchase #6	$123.51	7.628%	$132.9313	$132.93	$132.95	$132.90
Purchase #7	$211.76	13.131%	$239.5662	$239.57	$239.55	$239.60
7 purchase totals =	$850.32		$919.8933	$919.89	$919.90	$919.90