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	$123.93	5.516%	$130.766	$130.77	$130.75	$130.80
Purchase #2	$81.95	12.451%	$92.1536	$92.15	$92.15	$92.20
Purchase #3	$222.44	9.188%	$242.8778	$242.88	$242.90	$242.90
Purchase #4	$50.89	9.728%	$55.8406	$55.84	$55.85	$55.80
Purchase #5	$60.55	5.309%	$63.7646	$63.76	$63.75	$63.80
Purchase #6	$66.38	9.617%	$72.7638	$72.76	$72.75	$72.80
Purchase #7	$208.89	4.615%	$218.5303	$218.53	$218.55	$218.50
7 purchase totals =	$815.03		$876.6967	$876.69	$876.70	$876.80