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	$77.89	7.103%	$83.4225	$83.42	$83.40	$83.40
Purchase #2	$156.92	3.812%	$162.9018	$162.90	$162.90	$162.90
Purchase #3	$19.65	5.147%	$20.6614	$20.66	$20.65	$20.70
Purchase #4	$43.87	5.744%	$46.3899	$46.39	$46.40	$46.40
Purchase #5	$179.54	4.785%	$188.131	$188.13	$188.15	$188.10
Purchase #6	$191.65	11.166%	$213.0496	$213.05	$213.05	$213.00
Purchase #7	$76.93	12.468%	$86.5216	$86.52	$86.50	$86.50
7 purchase totals =	$746.45		$801.0778	$801.07	$801.05	$801.00