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	$54.74	10.715%	$60.6054	$60.61	$60.60	$60.60
Purchase #2	$84.89	3.584%	$87.9325	$87.93	$87.95	$87.90
Purchase #3	$223.83	5.623%	$236.416	$236.42	$236.40	$236.40
Purchase #4	$233.50	8.732%	$253.8892	$253.89	$253.90	$253.90
Purchase #5	$37.75	7.330%	$40.5171	$40.52	$40.50	$40.50
Purchase #6	$94.56	6.691%	$100.887	$100.89	$100.90	$100.90
Purchase #7	$49.62	10.282%	$54.7219	$54.72	$54.70	$54.70
7 purchase totals =	$778.89		$834.9691	$834.98	$834.95	$834.90