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	$55.34	4.504%	$57.8325	$57.83	$57.85	$57.80
Purchase #2	$10.88	10.300%	$12.0006	$12.00	$12.00	$12.00
Purchase #3	$239.54	6.475%	$255.0502	$255.05	$255.05	$255.10
Purchase #4	$200.30	9.768%	$219.8653	$219.87	$219.85	$219.90
Purchase #5	$207.47	7.751%	$223.551	$223.55	$223.55	$223.60
Purchase #6	$220.43	3.147%	$227.3669	$227.37	$227.35	$227.40
Purchase #7	$145.37	10.143%	$160.1149	$160.11	$160.10	$160.10
7 purchase totals =	$1,079.33		$1,155.7814	$1,155.78	$1,155.75	$1,155.90