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	$176.99	13.638%	$201.1279	$201.13	$201.15	$201.10
Purchase #2	$164.26	9.363%	$179.6397	$179.64	$179.65	$179.60
Purchase #3	$207.51	10.319%	$228.923	$228.92	$228.90	$228.90
Purchase #4	$123.33	6.455%	$131.291	$131.29	$131.30	$131.30
Purchase #5	$31.66	4.264%	$33.01	$33.01	$33.00	$33.00
Purchase #6	$101.82	7.550%	$109.5074	$109.51	$109.50	$109.50
Purchase #7	$35.89	11.807%	$40.1275	$40.13	$40.15	$40.10
7 purchase totals =	$841.46		$923.6265	$923.63	$923.65	$923.50