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	$77.61	6.813%	$82.8976	$82.90	$82.90	$82.90
Purchase #2	$54.36	6.725%	$58.0157	$58.02	$58.00	$58.00
Purchase #3	$121.32	5.323%	$127.7779	$127.78	$127.80	$127.80
Purchase #4	$10.67	10.396%	$11.7793	$11.78	$11.80	$11.80
Purchase #5	$138.80	11.598%	$154.898	$154.90	$154.90	$154.90
Purchase #6	$200.86	9.551%	$220.0441	$220.04	$220.05	$220.00
Purchase #7	$18.33	9.276%	$20.0303	$20.03	$20.05	$20.00
7 purchase totals =	$621.95		$675.4429	$675.45	$675.50	$675.40