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	$61.76	4.288%	$64.4083	$64.41	$64.40	$64.40
Purchase #2	$127.87	3.267%	$132.0475	$132.05	$132.05	$132.00
Purchase #3	$69.73	10.793%	$77.256	$77.26	$77.25	$77.30
Purchase #4	$156.93	12.521%	$176.5792	$176.58	$176.60	$176.60
Purchase #5	$38.47	11.581%	$42.9252	$42.93	$42.95	$42.90
Purchase #6	$17.76	6.347%	$18.8872	$18.89	$18.90	$18.90
Purchase #7	$76.36	11.653%	$85.2582	$85.26	$85.25	$85.30
7 purchase totals =	$548.88		$597.3616	$597.38	$597.40	$597.40