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	$17.77	3.312%	$18.3585	$18.36	$18.35	$18.40
Purchase #2	$83.88	3.713%	$86.9945	$86.99	$87.00	$87.00
Purchase #3	$171.42	7.672%	$184.5713	$184.57	$184.55	$184.60
Purchase #4	$196.48	9.601%	$215.344	$215.34	$215.35	$215.30
Purchase #5	$54.78	8.351%	$59.3547	$59.35	$59.35	$59.40
Purchase #6	$231.74	9.393%	$253.5073	$253.51	$253.50	$253.50
Purchase #7	$116.41	9.154%	$127.0662	$127.07	$127.05	$127.10
7 purchase totals =	$872.48		$945.1965	$945.19	$945.15	$945.30