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	$106.89	10.807%	$118.4416	$118.44	$118.45	$118.40
Purchase #2	$13.25	4.641%	$13.8649	$13.86	$13.85	$13.90
Purchase #3	$39.88	6.222%	$42.3613	$42.36	$42.35	$42.40
Purchase #4	$64.78	3.708%	$67.182	$67.18	$67.20	$67.20
Purchase #5	$101.38	9.635%	$111.148	$111.15	$111.15	$111.10
Purchase #6	$14.52	7.222%	$15.5686	$15.57	$15.55	$15.60
Purchase #7	$238.46	13.312%	$270.2038	$270.20	$270.20	$270.20
7 purchase totals =	$579.16		$638.7702	$638.76	$638.75	$638.80