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	$136.60	6.710%	$145.7659	$145.77	$145.75	$145.80
Purchase #2	$87.57	11.403%	$97.5556	$97.56	$97.55	$97.60
Purchase #3	$233.66	9.791%	$256.5377	$256.54	$256.55	$256.50
Purchase #4	$210.60	5.873%	$222.9685	$222.97	$222.95	$223.00
Purchase #5	$166.98	5.131%	$175.5477	$175.55	$175.55	$175.50
Purchase #6	$116.92	6.460%	$124.473	$124.47	$124.45	$124.50
Purchase #7	$106.94	12.117%	$119.8979	$119.90	$119.90	$119.90
7 purchase totals =	$1,059.27		$1,142.7463	$1,142.76	$1,142.70	$1,142.80