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	$84.71	4.582%	$88.5914	$88.59	$88.60	$88.60
Purchase #2	$48.54	4.802%	$50.8709	$50.87	$50.85	$50.90
Purchase #3	$150.96	5.255%	$158.8929	$158.89	$158.90	$158.90
Purchase #4	$47.35	11.851%	$52.9614	$52.96	$52.95	$53.00
Purchase #5	$229.71	9.290%	$251.0501	$251.05	$251.05	$251.10
Purchase #6	$37.91	7.861%	$40.8901	$40.89	$40.90	$40.90
Purchase #7	$57.45	10.598%	$63.5386	$63.54	$63.55	$63.50
7 purchase totals =	$656.63		$706.7954	$706.79	$706.80	$706.90