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	$126.50	4.214%	$131.8307	$131.83	$131.85	$131.80
Purchase #2	$58.64	4.184%	$61.0935	$61.09	$61.10	$61.10
Purchase #3	$172.67	4.847%	$181.0393	$181.04	$181.05	$181.00
Purchase #4	$31.87	4.274%	$33.2321	$33.23	$33.25	$33.20
Purchase #5	$208.81	7.527%	$224.5271	$224.53	$224.55	$224.50
Purchase #6	$46.78	11.820%	$52.3094	$52.31	$52.30	$52.30
Purchase #7	$58.67	9.580%	$64.2906	$64.29	$64.30	$64.30
7 purchase totals =	$703.94		$748.3227	$748.32	$748.40	$748.20