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	$63.54	9.253%	$69.4194	$69.42	$69.40	$69.40
Purchase #2	$159.62	5.667%	$168.6657	$168.67	$168.65	$168.70
Purchase #3	$119.71	7.422%	$128.5949	$128.59	$128.60	$128.60
Purchase #4	$163.76	13.319%	$185.5712	$185.57	$185.55	$185.60
Purchase #5	$242.64	10.622%	$268.4132	$268.41	$268.40	$268.40
Purchase #6	$148.46	8.289%	$160.7658	$160.77	$160.75	$160.80
Purchase #7	$137.25	9.497%	$150.2846	$150.28	$150.30	$150.30
7 purchase totals =	$1,034.98		$1,131.7148	$1,131.71	$1,131.65	$1,131.80