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	$106.59	3.551%	$110.375	$110.38	$110.40	$110.40
Purchase #2	$66.34	9.398%	$72.5746	$72.57	$72.55	$72.60
Purchase #3	$163.67	3.187%	$168.8862	$168.89	$168.90	$168.90
Purchase #4	$236.85	9.158%	$258.5407	$258.54	$258.55	$258.50
Purchase #5	$52.44	4.597%	$54.8507	$54.85	$54.85	$54.90
Purchase #6	$225.89	10.468%	$249.5362	$249.54	$249.55	$249.50
Purchase #7	$26.72	12.609%	$30.0891	$30.09	$30.10	$30.10
7 purchase totals =	$878.50		$944.8525	$944.86	$944.90	$944.90