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	$86.48	9.656%	$94.8305	$94.83	$94.85	$94.80
Purchase #2	$86.70	4.377%	$90.4949	$90.49	$90.50	$90.50
Purchase #3	$73.29	7.337%	$78.6673	$78.67	$78.65	$78.70
Purchase #4	$63.47	12.257%	$71.2495	$71.25	$71.25	$71.20
Purchase #5	$106.26	3.269%	$109.7336	$109.73	$109.75	$109.70
Purchase #6	$28.84	5.289%	$30.3653	$30.37	$30.35	$30.40
Purchase #7	$225.62	4.162%	$235.0103	$235.01	$235.00	$235.00
7 purchase totals =	$670.66		$710.3514	$710.35	$710.35	$710.30