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	$139.54	13.826%	$158.8328	$158.83	$158.85	$158.80
Purchase #2	$81.59	6.780%	$87.1218	$87.12	$87.10	$87.10
Purchase #3	$154.87	5.154%	$162.852	$162.85	$162.85	$162.90
Purchase #4	$57.40	12.338%	$64.482	$64.48	$64.50	$64.50
Purchase #5	$139.27	3.342%	$143.9244	$143.92	$143.90	$143.90
Purchase #6	$167.98	11.229%	$186.8425	$186.84	$186.85	$186.80
Purchase #7	$64.71	4.306%	$67.4964	$67.50	$67.50	$67.50
7 purchase totals =	$805.36		$871.5519	$871.54	$871.55	$871.50