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	$82.26	4.584%	$86.0308	$86.03	$86.05	$86.00
Purchase #2	$127.80	3.271%	$131.9803	$131.98	$132.00	$132.00
Purchase #3	$150.64	9.462%	$164.8936	$164.89	$164.90	$164.90
Purchase #4	$84.39	5.832%	$89.3116	$89.31	$89.30	$89.30
Purchase #5	$141.46	7.787%	$152.4755	$152.48	$152.50	$152.50
Purchase #6	$25.54	8.625%	$27.7428	$27.74	$27.75	$27.70
Purchase #7	$83.63	6.524%	$89.086	$89.09	$89.10	$89.10
7 purchase totals =	$695.72		$741.5206	$741.52	$741.60	$741.50