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	$184.64	6.195%	$196.0784	$196.08	$196.10	$196.10
Purchase #2	$96.34	8.529%	$104.5568	$104.56	$104.55	$104.60
Purchase #3	$217.89	9.145%	$237.816	$237.82	$237.80	$237.80
Purchase #4	$16.26	9.330%	$17.7771	$17.78	$17.80	$17.80
Purchase #5	$31.45	3.322%	$32.4948	$32.49	$32.50	$32.50
Purchase #6	$94.47	10.643%	$104.5244	$104.52	$104.50	$104.50
Purchase #7	$79.36	5.409%	$83.6526	$83.65	$83.65	$83.70
7 purchase totals =	$720.41		$776.9001	$776.90	$776.90	$777.00