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	$127.55	13.469%	$144.7297	$144.73	$144.75	$144.70
Purchase #2	$214.26	8.804%	$233.1235	$233.12	$233.10	$233.10
Purchase #3	$140.43	7.127%	$150.4384	$150.44	$150.45	$150.40
Purchase #4	$102.41	12.767%	$115.4847	$115.48	$115.50	$115.50
Purchase #5	$102.54	6.738%	$109.4491	$109.45	$109.45	$109.40
Purchase #6	$87.93	13.663%	$99.9439	$99.94	$99.95	$99.90
Purchase #7	$80.94	8.153%	$87.539	$87.54	$87.55	$87.50
7 purchase totals =	$856.06		$940.7083	$940.70	$940.75	$940.50