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	$171.87	6.207%	$182.538	$182.54	$182.55	$182.50
Purchase #2	$88.61	13.745%	$100.7894	$100.79	$100.80	$100.80
Purchase #3	$24.76	4.553%	$25.8873	$25.89	$25.90	$25.90
Purchase #4	$189.67	9.259%	$207.2315	$207.23	$207.25	$207.20
Purchase #5	$224.72	13.844%	$255.8302	$255.83	$255.85	$255.80
Purchase #6	$75.63	4.320%	$78.8972	$78.90	$78.90	$78.90
Purchase #7	$141.90	7.138%	$152.0288	$152.03	$152.05	$152.00
7 purchase totals =	$917.16		$1,003.2024	$1,003.21	$1,003.30	$1,003.10