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	$184.37	11.136%	$204.9014	$204.90	$204.90	$204.90
Purchase #2	$95.94	9.252%	$104.8164	$104.82	$104.80	$104.80
Purchase #3	$153.27	11.626%	$171.0892	$171.09	$171.10	$171.10
Purchase #4	$190.48	3.259%	$196.6877	$196.69	$196.70	$196.70
Purchase #5	$228.28	9.718%	$250.4643	$250.46	$250.45	$250.50
Purchase #6	$175.50	6.443%	$186.8075	$186.81	$186.80	$186.80
Purchase #7	$96.49	3.337%	$99.7099	$99.71	$99.70	$99.70
7 purchase totals =	$1,124.33		$1,214.4764	$1,214.48	$1,214.45	$1,214.50