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	$165.45	3.769%	$171.6858	$171.69	$171.70	$171.70
Purchase #2	$231.44	13.543%	$262.7839	$262.78	$262.80	$262.80
Purchase #3	$178.81	4.282%	$186.4666	$186.47	$186.45	$186.50
Purchase #4	$38.78	7.465%	$41.6749	$41.67	$41.65	$41.70
Purchase #5	$224.51	8.171%	$242.8547	$242.85	$242.85	$242.90
Purchase #6	$89.64	11.406%	$99.8643	$99.86	$99.85	$99.90
Purchase #7	$226.66	10.116%	$249.5889	$249.59	$249.60	$249.60
7 purchase totals =	$1,155.29		$1,254.9191	$1,254.91	$1,254.90	$1,255.10