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	$80.28	11.545%	$89.5483	$89.55	$89.55	$89.50
Purchase #2	$32.49	3.528%	$33.6362	$33.64	$33.65	$33.60
Purchase #3	$151.32	8.292%	$163.8675	$163.87	$163.85	$163.90
Purchase #4	$94.41	10.684%	$104.4968	$104.50	$104.50	$104.50
Purchase #5	$221.43	9.766%	$243.0549	$243.05	$243.05	$243.10
Purchase #6	$168.96	11.424%	$188.262	$188.26	$188.25	$188.30
Purchase #7	$105.28	11.609%	$117.502	$117.50	$117.50	$117.50
7 purchase totals =	$854.17		$940.3677	$940.37	$940.35	$940.40