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	$116.89	8.831%	$127.2126	$127.21	$127.20	$127.20
Purchase #2	$127.27	9.485%	$139.3416	$139.34	$139.35	$139.30
Purchase #3	$148.40	9.473%	$162.4579	$162.46	$162.45	$162.50
Purchase #4	$133.78	10.291%	$147.5473	$147.55	$147.55	$147.50
Purchase #5	$150.59	5.355%	$158.6541	$158.65	$158.65	$158.70
Purchase #6	$8.72	9.788%	$9.5735	$9.57	$9.55	$9.60
Purchase #7	$37.35	10.122%	$41.1306	$41.13	$41.15	$41.10
7 purchase totals =	$723.00		$785.9176	$785.91	$785.90	$785.90