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	$200.33	11.785%	$223.9389	$223.94	$223.95	$223.90
Purchase #2	$112.60	5.769%	$119.0959	$119.10	$119.10	$119.10
Purchase #3	$51.97	9.604%	$56.9612	$56.96	$56.95	$57.00
Purchase #4	$17.34	5.552%	$18.3027	$18.30	$18.30	$18.30
Purchase #5	$223.40	4.793%	$234.1076	$234.11	$234.10	$234.10
Purchase #6	$85.48	5.665%	$90.3224	$90.32	$90.30	$90.30
Purchase #7	$83.86	4.520%	$87.6505	$87.65	$87.65	$87.70
7 purchase totals =	$774.98		$830.3792	$830.38	$830.35	$830.40