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	$75.53	10.562%	$83.5075	$83.51	$83.50	$83.50
Purchase #2	$96.43	4.223%	$100.5022	$100.50	$100.50	$100.50
Purchase #3	$96.67	3.632%	$100.1811	$100.18	$100.20	$100.20
Purchase #4	$134.85	11.264%	$150.0395	$150.04	$150.05	$150.00
Purchase #5	$241.71	13.502%	$274.3457	$274.35	$274.35	$274.30
Purchase #6	$55.44	6.197%	$58.8756	$58.88	$58.90	$58.90
Purchase #7	$168.81	11.266%	$187.8281	$187.83	$187.85	$187.80
7 purchase totals =	$869.44		$955.2797	$955.29	$955.35	$955.20