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	$66.43	3.161%	$68.5299	$68.53	$68.55	$68.50
Purchase #2	$244.99	9.190%	$267.5046	$267.50	$267.50	$267.50
Purchase #3	$171.87	10.867%	$190.5471	$190.55	$190.55	$190.50
Purchase #4	$149.61	12.803%	$168.7646	$168.76	$168.75	$168.80
Purchase #5	$14.25	11.604%	$15.9036	$15.90	$15.90	$15.90
Purchase #6	$196.27	10.519%	$216.9156	$216.92	$216.90	$216.90
Purchase #7	$116.34	13.674%	$132.2483	$132.25	$132.25	$132.20
7 purchase totals =	$959.76		$1,060.4137	$1,060.41	$1,060.40	$1,060.30