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	$67.67	5.370%	$71.3039	$71.30	$71.30	$71.30
Purchase #2	$210.32	3.680%	$218.0598	$218.06	$218.05	$218.10
Purchase #3	$80.79	6.418%	$85.9751	$85.98	$86.00	$86.00
Purchase #4	$178.31	5.241%	$187.6552	$187.66	$187.65	$187.70
Purchase #5	$60.32	9.142%	$65.8345	$65.83	$65.85	$65.80
Purchase #6	$247.83	3.704%	$257.0096	$257.01	$257.00	$257.00
Purchase #7	$37.77	7.498%	$40.602	$40.60	$40.60	$40.60
7 purchase totals =	$883.01		$926.4401	$926.44	$926.45	$926.50