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	$57.54	3.382%	$59.486	$59.49	$59.50	$59.50
Purchase #2	$159.89	7.260%	$171.498	$171.50	$171.50	$171.50
Purchase #3	$110.73	7.584%	$119.1278	$119.13	$119.15	$119.10
Purchase #4	$241.53	12.337%	$271.3276	$271.33	$271.35	$271.30
Purchase #5	$228.39	7.823%	$246.2569	$246.26	$246.25	$246.30
Purchase #6	$137.91	9.387%	$150.8556	$150.86	$150.85	$150.90
Purchase #7	$64.63	5.289%	$68.0483	$68.05	$68.05	$68.00
7 purchase totals =	$1,000.62		$1,086.6002	$1,086.62	$1,086.65	$1,086.60