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	$104.59	7.829%	$112.7784	$112.78	$112.80	$112.80
Purchase #2	$203.85	13.657%	$231.6898	$231.69	$231.70	$231.70
Purchase #3	$86.54	3.189%	$89.2998	$89.30	$89.30	$89.30
Purchase #4	$235.86	5.874%	$249.7144	$249.71	$249.70	$249.70
Purchase #5	$239.73	10.370%	$264.59	$264.59	$264.60	$264.60
Purchase #6	$175.92	4.583%	$183.9824	$183.98	$184.00	$184.00
Purchase #7	$25.72	10.329%	$28.3766	$28.38	$28.40	$28.40
7 purchase totals =	$1,072.21		$1,160.4314	$1,160.43	$1,160.50	$1,160.50