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	$80.65	6.177%	$85.6318	$85.63	$85.65	$85.60
Purchase #2	$64.71	6.456%	$68.8877	$68.89	$68.90	$68.90
Purchase #3	$133.98	10.507%	$148.0573	$148.06	$148.05	$148.10
Purchase #4	$240.77	4.177%	$250.827	$250.83	$250.85	$250.80
Purchase #5	$135.76	12.270%	$152.4178	$152.42	$152.40	$152.40
Purchase #6	$39.45	3.568%	$40.8576	$40.86	$40.85	$40.90
Purchase #7	$190.48	7.689%	$205.126	$205.13	$205.15	$205.10
7 purchase totals =	$885.80		$951.8052	$951.82	$951.85	$951.80