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	$142.84	5.636%	$150.8905	$150.89	$150.90	$150.90
Purchase #2	$210.46	3.191%	$217.1758	$217.18	$217.20	$217.20
Purchase #3	$45.27	9.401%	$49.5258	$49.53	$49.55	$49.50
Purchase #4	$79.26	4.243%	$82.623	$82.62	$82.60	$82.60
Purchase #5	$166.40	10.802%	$184.3745	$184.37	$184.35	$184.40
Purchase #6	$174.67	12.491%	$196.488	$196.49	$196.50	$196.50
Purchase #7	$46.55	11.250%	$51.7869	$51.79	$51.80	$51.80
7 purchase totals =	$865.45		$932.8645	$932.87	$932.90	$932.90