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	$117.95	6.708%	$125.8621	$125.86	$125.85	$125.90
Purchase #2	$110.40	3.759%	$114.5499	$114.55	$114.55	$114.50
Purchase #3	$244.52	10.757%	$270.823	$270.82	$270.80	$270.80
Purchase #4	$136.76	5.498%	$144.2791	$144.28	$144.30	$144.30
Purchase #5	$36.32	3.743%	$37.6795	$37.68	$37.70	$37.70
Purchase #6	$176.46	11.482%	$196.7211	$196.72	$196.70	$196.70
Purchase #7	$58.64	13.200%	$66.3805	$66.38	$66.40	$66.40
7 purchase totals =	$881.05		$956.2952	$956.29	$956.30	$956.30