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	$191.55	5.804%	$202.6676	$202.67	$202.65	$202.70
Purchase #2	$227.50	5.189%	$239.305	$239.31	$239.30	$239.30
Purchase #3	$142.27	5.490%	$150.0806	$150.08	$150.10	$150.10
Purchase #4	$243.43	6.763%	$259.8932	$259.89	$259.90	$259.90
Purchase #5	$151.26	10.792%	$167.584	$167.58	$167.60	$167.60
Purchase #6	$79.43	12.665%	$89.4898	$89.49	$89.50	$89.50
Purchase #7	$91.31	13.780%	$103.8925	$103.89	$103.90	$103.90
7 purchase totals =	$1,126.75		$1,212.9127	$1,212.91	$1,212.95	$1,213.00