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	$129.93	10.426%	$143.4765	$143.48	$143.50	$143.50
Purchase #2	$84.64	12.755%	$95.4358	$95.44	$95.45	$95.40
Purchase #3	$33.74	10.459%	$37.2689	$37.27	$37.25	$37.30
Purchase #4	$75.89	3.547%	$78.5818	$78.58	$78.60	$78.60
Purchase #5	$204.82	12.223%	$229.8551	$229.86	$229.85	$229.90
Purchase #6	$40.75	7.640%	$43.8633	$43.86	$43.85	$43.90
Purchase #7	$226.76	3.661%	$235.0617	$235.06	$235.05	$235.10
7 purchase totals =	$796.53		$863.5431	$863.55	$863.55	$863.70