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	$148.73	10.703%	$164.6486	$164.65	$164.65	$164.60
Purchase #2	$202.64	9.209%	$221.3011	$221.30	$221.30	$221.30
Purchase #3	$247.28	7.719%	$266.3675	$266.37	$266.35	$266.40
Purchase #4	$117.67	7.526%	$126.5258	$126.53	$126.55	$126.50
Purchase #5	$54.29	9.620%	$59.5127	$59.51	$59.50	$59.50
Purchase #6	$248.47	3.297%	$256.6621	$256.66	$256.65	$256.70
Purchase #7	$46.52	6.139%	$49.3759	$49.38	$49.40	$49.40
7 purchase totals =	$1,065.60		$1,144.3937	$1,144.40	$1,144.40	$1,144.40