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	$102.56	13.657%	$116.5666	$116.57	$116.55	$116.60
Purchase #2	$196.73	7.178%	$210.8513	$210.85	$210.85	$210.90
Purchase #3	$63.65	5.787%	$67.3334	$67.33	$67.35	$67.30
Purchase #4	$120.27	5.215%	$126.5421	$126.54	$126.55	$126.50
Purchase #5	$65.40	8.719%	$71.1022	$71.10	$71.10	$71.10
Purchase #6	$175.96	6.756%	$187.8479	$187.85	$187.85	$187.80
Purchase #7	$184.87	13.500%	$209.8275	$209.83	$209.85	$209.80
7 purchase totals =	$909.44		$990.0710	$990.07	$990.10	$990.00