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	$76.72	12.610%	$86.3944	$86.39	$86.40	$86.40
Purchase #2	$182.48	12.393%	$205.0947	$205.09	$205.10	$205.10
Purchase #3	$67.72	7.420%	$72.7448	$72.74	$72.75	$72.70
Purchase #4	$53.27	5.869%	$56.3964	$56.40	$56.40	$56.40
Purchase #5	$174.44	9.197%	$190.4832	$190.48	$190.50	$190.50
Purchase #6	$161.53	12.302%	$181.4014	$181.40	$181.40	$181.40
Purchase #7	$169.66	5.449%	$178.9048	$178.90	$178.90	$178.90
7 purchase totals =	$885.82		$971.4197	$971.40	$971.45	$971.40