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	$101.70	11.139%	$113.0284	$113.03	$113.05	$113.00
Purchase #2	$32.33	9.821%	$35.5051	$35.51	$35.50	$35.50
Purchase #3	$130.29	7.708%	$140.3328	$140.33	$140.35	$140.30
Purchase #4	$196.49	8.774%	$213.73	$213.73	$213.75	$213.70
Purchase #5	$113.95	8.664%	$123.8226	$123.82	$123.80	$123.80
Purchase #6	$176.98	13.457%	$200.7962	$200.80	$200.80	$200.80
Purchase #7	$78.87	13.505%	$89.5214	$89.52	$89.50	$89.50
7 purchase totals =	$830.61		$916.7365	$916.74	$916.75	$916.60