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	$48.92	9.573%	$53.6031	$53.60	$53.60	$53.60
Purchase #2	$156.88	9.120%	$171.1875	$171.19	$171.20	$171.20
Purchase #3	$234.56	13.225%	$265.5806	$265.58	$265.60	$265.60
Purchase #4	$91.33	7.391%	$98.0802	$98.08	$98.10	$98.10
Purchase #5	$112.51	6.551%	$119.8805	$119.88	$119.90	$119.90
Purchase #6	$249.73	12.661%	$281.3483	$281.35	$281.35	$281.30
Purchase #7	$189.82	3.527%	$196.515	$196.52	$196.50	$196.50
7 purchase totals =	$1,083.75		$1,186.1952	$1,186.20	$1,186.25	$1,186.20