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	$199.30	5.762%	$210.7837	$210.78	$210.80	$210.80
Purchase #2	$104.92	3.578%	$108.674	$108.67	$108.65	$108.70
Purchase #3	$128.76	7.105%	$137.9084	$137.91	$137.90	$137.90
Purchase #4	$33.90	10.392%	$37.4229	$37.42	$37.40	$37.40
Purchase #5	$154.83	9.111%	$168.9366	$168.94	$168.95	$168.90
Purchase #6	$101.59	13.555%	$115.3605	$115.36	$115.35	$115.40
Purchase #7	$228.27	7.791%	$246.0545	$246.05	$246.05	$246.10
7 purchase totals =	$951.57		$1,025.1406	$1,025.13	$1,025.10	$1,025.20