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	$179.65	6.624%	$191.55	$191.55	$191.55	$191.60
Purchase #2	$56.90	12.146%	$63.8111	$63.81	$63.80	$63.80
Purchase #3	$77.58	9.503%	$84.9524	$84.95	$84.95	$85.00
Purchase #4	$46.69	8.500%	$50.6587	$50.66	$50.65	$50.70
Purchase #5	$190.82	4.832%	$200.0404	$200.04	$200.05	$200.00
Purchase #6	$56.73	5.317%	$59.7463	$59.75	$59.75	$59.70
Purchase #7	$163.95	4.674%	$171.613	$171.61	$171.60	$171.60
7 purchase totals =	$772.32		$822.3719	$822.37	$822.35	$822.40