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	$62.29	11.824%	$69.6552	$69.66	$69.65	$69.70
Purchase #2	$238.35	9.233%	$260.3569	$260.36	$260.35	$260.40
Purchase #3	$34.62	3.662%	$35.8878	$35.89	$35.90	$35.90
Purchase #4	$53.50	4.234%	$55.7652	$55.77	$55.75	$55.80
Purchase #5	$83.28	7.865%	$89.83	$89.83	$89.85	$89.80
Purchase #6	$200.31	12.315%	$224.9782	$224.98	$225.00	$225.00
Purchase #7	$233.45	9.715%	$256.1297	$256.13	$256.15	$256.10
7 purchase totals =	$905.80		$992.6030	$992.62	$992.65	$992.70