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	$217.73	6.148%	$231.116	$231.12	$231.10	$231.10
Purchase #2	$44.33	4.863%	$46.4858	$46.49	$46.50	$46.50
Purchase #3	$193.30	9.415%	$211.4992	$211.50	$211.50	$211.50
Purchase #4	$74.73	5.547%	$78.8753	$78.88	$78.90	$78.90
Purchase #5	$64.58	10.548%	$71.3919	$71.39	$71.40	$71.40
Purchase #6	$117.60	4.612%	$123.0237	$123.02	$123.00	$123.00
Purchase #7	$93.48	5.758%	$98.8626	$98.86	$98.85	$98.90
7 purchase totals =	$805.75		$861.2545	$861.26	$861.25	$861.30