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	$102.25	10.522%	$113.0087	$113.01	$113.00	$113.00
Purchase #2	$30.31	9.369%	$33.1497	$33.15	$33.15	$33.10
Purchase #3	$210.28	8.493%	$228.1391	$228.14	$228.15	$228.10
Purchase #4	$223.89	10.741%	$247.938	$247.94	$247.95	$247.90
Purchase #5	$146.29	12.425%	$164.4665	$164.47	$164.45	$164.50
Purchase #6	$219.48	11.866%	$245.5235	$245.52	$245.50	$245.50
Purchase #7	$61.29	11.644%	$68.4266	$68.43	$68.45	$68.40
7 purchase totals =	$993.79		$1,100.6521	$1,100.66	$1,100.65	$1,100.50