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	$174.65	12.522%	$196.5197	$196.52	$196.50	$196.50
Purchase #2	$112.47	6.156%	$119.3937	$119.39	$119.40	$119.40
Purchase #3	$223.33	11.214%	$248.3742	$248.37	$248.35	$248.40
Purchase #4	$161.36	4.406%	$168.4695	$168.47	$168.45	$168.50
Purchase #5	$131.55	4.547%	$137.5316	$137.53	$137.55	$137.50
Purchase #6	$62.57	9.534%	$68.5354	$68.54	$68.55	$68.50
Purchase #7	$225.49	10.709%	$249.6377	$249.64	$249.65	$249.60
7 purchase totals =	$1,091.42		$1,188.4618	$1,188.46	$1,188.45	$1,188.40