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	$133.32	7.193%	$142.9097	$142.91	$142.90	$142.90
Purchase #2	$37.69	11.376%	$41.9776	$41.98	$42.00	$42.00
Purchase #3	$145.93	12.426%	$164.0633	$164.06	$164.05	$164.10
Purchase #4	$246.48	13.252%	$279.1435	$279.14	$279.15	$279.10
Purchase #5	$142.56	3.277%	$147.2317	$147.23	$147.25	$147.20
Purchase #6	$19.93	7.812%	$21.4869	$21.49	$21.50	$21.50
Purchase #7	$217.49	11.850%	$243.2626	$243.26	$243.25	$243.30
7 purchase totals =	$943.40		$1,040.0753	$1,040.07	$1,040.10	$1,040.10