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	$174.27	12.760%	$196.5069	$196.51	$196.50	$196.50
Purchase #2	$38.34	4.652%	$40.1236	$40.12	$40.10	$40.10
Purchase #3	$20.87	13.221%	$23.6292	$23.63	$23.65	$23.60
Purchase #4	$103.98	8.617%	$112.94	$112.94	$112.95	$112.90
Purchase #5	$82.77	11.462%	$92.2571	$92.26	$92.25	$92.30
Purchase #6	$165.96	8.332%	$179.7878	$179.79	$179.80	$179.80
Purchase #7	$168.53	4.392%	$175.9318	$175.93	$175.95	$175.90
7 purchase totals =	$754.72		$821.1764	$821.18	$821.20	$821.10