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	$209.43	3.223%	$216.1799	$216.18	$216.20	$216.20
Purchase #2	$250.89	9.329%	$274.2955	$274.30	$274.30	$274.30
Purchase #3	$191.36	12.664%	$215.5938	$215.59	$215.60	$215.60
Purchase #4	$142.66	10.686%	$157.9046	$157.90	$157.90	$157.90
Purchase #5	$9.82	9.361%	$10.7393	$10.74	$10.75	$10.70
Purchase #6	$32.60	13.854%	$37.1164	$37.12	$37.10	$37.10
Purchase #7	$119.69	9.748%	$131.3574	$131.36	$131.35	$131.40
7 purchase totals =	$956.45		$1,043.1869	$1,043.19	$1,043.20	$1,043.20