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	$61.79	9.440%	$67.623	$67.62	$67.60	$67.60
Purchase #2	$168.53	6.555%	$179.5771	$179.58	$179.60	$179.60
Purchase #3	$124.44	5.603%	$131.4124	$131.41	$131.40	$131.40
Purchase #4	$127.91	10.248%	$141.0182	$141.02	$141.00	$141.00
Purchase #5	$211.93	13.500%	$240.5406	$240.54	$240.55	$240.50
Purchase #6	$104.28	4.695%	$109.1759	$109.18	$109.20	$109.20
Purchase #7	$82.60	3.193%	$85.2374	$85.24	$85.25	$85.20
7 purchase totals =	$881.48		$954.5846	$954.59	$954.60	$954.50