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	$141.49	10.164%	$155.871	$155.87	$155.85	$155.90
Purchase #2	$237.87	13.582%	$270.1775	$270.18	$270.20	$270.20
Purchase #3	$208.73	6.418%	$222.1263	$222.13	$222.15	$222.10
Purchase #4	$134.78	13.128%	$152.4739	$152.47	$152.45	$152.50
Purchase #5	$105.39	3.475%	$109.0523	$109.05	$109.05	$109.10
Purchase #6	$130.30	8.438%	$141.2947	$141.29	$141.30	$141.30
Purchase #7	$113.57	11.237%	$126.3319	$126.33	$126.35	$126.30
7 purchase totals =	$1,072.13		$1,177.3276	$1,177.32	$1,177.35	$1,177.40