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	$83.97	11.330%	$93.4838	$93.48	$93.50	$93.50
Purchase #2	$205.43	7.529%	$220.8968	$220.90	$220.90	$220.90
Purchase #3	$176.34	5.158%	$185.4356	$185.44	$185.45	$185.40
Purchase #4	$222.72	7.465%	$239.346	$239.35	$239.35	$239.30
Purchase #5	$113.30	9.354%	$123.8981	$123.90	$123.90	$123.90
Purchase #6	$82.69	7.144%	$88.5974	$88.60	$88.60	$88.60
Purchase #7	$150.70	11.674%	$168.2927	$168.29	$168.30	$168.30
7 purchase totals =	$1,035.15		$1,119.9504	$1,119.96	$1,120.00	$1,119.90