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	$185.75	6.440%	$197.7123	$197.71	$197.70	$197.70
Purchase #2	$114.59	11.183%	$127.4046	$127.40	$127.40	$127.40
Purchase #3	$237.71	9.222%	$259.6316	$259.63	$259.65	$259.60
Purchase #4	$201.71	12.518%	$226.9601	$226.96	$226.95	$227.00
Purchase #5	$64.70	12.548%	$72.8186	$72.82	$72.80	$72.80
Purchase #6	$57.65	3.541%	$59.6914	$59.69	$59.70	$59.70
Purchase #7	$85.41	5.763%	$90.3322	$90.33	$90.35	$90.30
7 purchase totals =	$947.52		$1,034.5508	$1,034.54	$1,034.55	$1,034.50