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	$205.65	12.550%	$231.4591	$231.46	$231.45	$231.50
Purchase #2	$74.96	9.789%	$82.2978	$82.30	$82.30	$82.30
Purchase #3	$143.90	12.658%	$162.1149	$162.11	$162.10	$162.10
Purchase #4	$212.89	10.166%	$234.5324	$234.53	$234.55	$234.50
Purchase #5	$171.49	13.446%	$194.5485	$194.55	$194.55	$194.50
Purchase #6	$126.92	12.626%	$142.9449	$142.94	$142.95	$142.90
Purchase #7	$137.98	10.699%	$152.7425	$152.74	$152.75	$152.70
7 purchase totals =	$1,073.79		$1,200.6401	$1,200.63	$1,200.65	$1,200.50