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	$67.51	10.584%	$74.6553	$74.66	$74.65	$74.70
Purchase #2	$40.38	13.223%	$45.7194	$45.72	$45.70	$45.70
Purchase #3	$91.95	6.447%	$97.878	$97.88	$97.90	$97.90
Purchase #4	$81.49	10.848%	$90.33	$90.33	$90.35	$90.30
Purchase #5	$51.80	9.808%	$56.8805	$56.88	$56.90	$56.90
Purchase #6	$141.48	12.564%	$159.2555	$159.26	$159.25	$159.30
Purchase #7	$82.96	13.415%	$94.0891	$94.09	$94.10	$94.10
7 purchase totals =	$557.57		$618.8078	$618.82	$618.85	$618.90