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	$157.85	4.179%	$164.4466	$164.45	$164.45	$164.40
Purchase #2	$90.38	13.308%	$102.4078	$102.41	$102.40	$102.40
Purchase #3	$164.43	6.553%	$175.2051	$175.21	$175.20	$175.20
Purchase #4	$91.56	9.120%	$99.9103	$99.91	$99.90	$99.90
Purchase #5	$218.52	7.279%	$234.4261	$234.43	$234.45	$234.40
Purchase #6	$11.29	10.825%	$12.5121	$12.51	$12.50	$12.50
Purchase #7	$138.25	9.193%	$150.9593	$150.96	$150.95	$151.00
7 purchase totals =	$872.28		$939.8673	$939.88	$939.85	$939.80