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	$96.32	8.492%	$104.4995	$104.50	$104.50	$104.50
Purchase #2	$6.37	12.382%	$7.1587	$7.16	$7.15	$7.20
Purchase #3	$109.73	13.819%	$124.8936	$124.89	$124.90	$124.90
Purchase #4	$76.96	11.722%	$85.9813	$85.98	$86.00	$86.00
Purchase #5	$164.80	12.541%	$185.4676	$185.47	$185.45	$185.50
Purchase #6	$27.59	11.388%	$30.7319	$30.73	$30.75	$30.70
Purchase #7	$134.29	9.196%	$146.6393	$146.64	$146.65	$146.60
7 purchase totals =	$616.06		$685.3719	$685.37	$685.40	$685.40