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	$229.43	11.188%	$255.0986	$255.10	$255.10	$255.10
Purchase #2	$111.96	5.600%	$118.2298	$118.23	$118.25	$118.20
Purchase #3	$10.92	3.761%	$11.3307	$11.33	$11.35	$11.30
Purchase #4	$154.40	9.341%	$168.8225	$168.82	$168.80	$168.80
Purchase #5	$76.76	10.590%	$84.8889	$84.89	$84.90	$84.90
Purchase #6	$160.35	9.825%	$176.1044	$176.10	$176.10	$176.10
Purchase #7	$211.52	8.450%	$229.3934	$229.39	$229.40	$229.40
7 purchase totals =	$955.34		$1,043.8683	$1,043.86	$1,043.90	$1,043.80