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	$181.95	10.389%	$200.8528	$200.85	$200.85	$200.90
Purchase #2	$39.26	10.730%	$43.4726	$43.47	$43.45	$43.50
Purchase #3	$219.89	4.333%	$229.4178	$229.42	$229.40	$229.40
Purchase #4	$108.99	11.266%	$121.2688	$121.27	$121.25	$121.30
Purchase #5	$215.65	8.752%	$234.5237	$234.52	$234.50	$234.50
Purchase #6	$44.89	12.425%	$50.4676	$50.47	$50.45	$50.50
Purchase #7	$139.73	3.851%	$145.111	$145.11	$145.10	$145.10
7 purchase totals =	$950.36		$1,025.1143	$1,025.11	$1,025.00	$1,025.20