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	$184.59	12.807%	$208.2304	$208.23	$208.25	$208.20
Purchase #2	$10.60	5.136%	$11.1444	$11.14	$11.15	$11.10
Purchase #3	$142.26	9.371%	$155.5912	$155.59	$155.60	$155.60
Purchase #4	$189.40	10.516%	$209.3173	$209.32	$209.30	$209.30
Purchase #5	$239.51	4.189%	$249.5431	$249.54	$249.55	$249.50
Purchase #6	$105.48	6.279%	$112.1031	$112.10	$112.10	$112.10
Purchase #7	$56.26	11.808%	$62.9032	$62.90	$62.90	$62.90
7 purchase totals =	$928.10		$1,008.8327	$1,008.82	$1,008.85	$1,008.70