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	$145.29	13.593%	$165.0393	$165.04	$165.05	$165.00
Purchase #2	$109.25	7.853%	$117.8294	$117.83	$117.85	$117.80
Purchase #3	$178.36	3.870%	$185.2625	$185.26	$185.25	$185.30
Purchase #4	$218.38	12.402%	$245.4635	$245.46	$245.45	$245.50
Purchase #5	$90.38	9.127%	$98.629	$98.63	$98.65	$98.60
Purchase #6	$78.45	11.585%	$87.5384	$87.54	$87.55	$87.50
Purchase #7	$60.26	8.124%	$65.1555	$65.16	$65.15	$65.20
7 purchase totals =	$880.37		$964.9176	$964.92	$964.95	$964.90