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	$179.53	12.102%	$201.2567	$201.26	$201.25	$201.30
Purchase #2	$216.48	12.473%	$243.4816	$243.48	$243.50	$243.50
Purchase #3	$105.77	8.159%	$114.3998	$114.40	$114.40	$114.40
Purchase #4	$102.74	6.106%	$109.0133	$109.01	$109.00	$109.00
Purchase #5	$143.74	8.363%	$155.761	$155.76	$155.75	$155.80
Purchase #6	$174.29	12.598%	$196.2471	$196.25	$196.25	$196.20
Purchase #7	$60.78	9.576%	$66.6003	$66.60	$66.60	$66.60
7 purchase totals =	$983.33		$1,086.7598	$1,086.76	$1,086.75	$1,086.80