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	$52.50	12.447%	$59.0347	$59.03	$59.05	$59.00
Purchase #2	$32.75	9.568%	$35.8835	$35.88	$35.90	$35.90
Purchase #3	$88.86	6.641%	$94.7612	$94.76	$94.75	$94.80
Purchase #4	$93.35	6.547%	$99.4616	$99.46	$99.45	$99.50
Purchase #5	$95.97	9.439%	$105.0286	$105.03	$105.05	$105.00
Purchase #6	$28.33	4.796%	$29.6887	$29.69	$29.70	$29.70
Purchase #7	$197.95	8.552%	$214.8787	$214.88	$214.90	$214.90
7 purchase totals =	$589.71		$638.7370	$638.73	$638.80	$638.80