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	$54.61	8.356%	$59.1732	$59.17	$59.15	$59.20
Purchase #2	$152.78	4.429%	$159.5466	$159.55	$159.55	$159.50
Purchase #3	$198.86	11.586%	$221.8999	$221.90	$221.90	$221.90
Purchase #4	$163.86	11.371%	$182.4925	$182.49	$182.50	$182.50
Purchase #5	$80.93	5.136%	$85.0866	$85.09	$85.10	$85.10
Purchase #6	$9.44	9.856%	$10.3704	$10.37	$10.35	$10.40
Purchase #7	$130.76	13.368%	$148.24	$148.24	$148.25	$148.20
7 purchase totals =	$791.24		$866.8092	$866.81	$866.80	$866.80