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	$52.26	13.458%	$59.2932	$59.29	$59.30	$59.30
Purchase #2	$207.98	11.400%	$231.6897	$231.69	$231.70	$231.70
Purchase #3	$133.83	6.521%	$142.5571	$142.56	$142.55	$142.60
Purchase #4	$30.67	4.438%	$32.0311	$32.03	$32.05	$32.00
Purchase #5	$5.69	11.110%	$6.3222	$6.32	$6.30	$6.30
Purchase #6	$135.51	12.204%	$152.0476	$152.05	$152.05	$152.00
Purchase #7	$104.38	4.513%	$109.0907	$109.09	$109.10	$109.10
7 purchase totals =	$670.32		$733.0316	$733.03	$733.05	$733.00