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	$63.68	13.764%	$72.4449	$72.44	$72.45	$72.40
Purchase #2	$116.28	8.173%	$125.7836	$125.78	$125.80	$125.80
Purchase #3	$16.90	7.796%	$18.2175	$18.22	$18.20	$18.20
Purchase #4	$180.36	4.695%	$188.8279	$188.83	$188.85	$188.80
Purchase #5	$127.76	12.536%	$143.776	$143.78	$143.80	$143.80
Purchase #6	$212.41	4.785%	$222.5738	$222.57	$222.55	$222.60
Purchase #7	$27.88	5.673%	$29.4616	$29.46	$29.45	$29.50
7 purchase totals =	$745.27		$801.0853	$801.08	$801.10	$801.10