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	$143.75	5.340%	$151.4263	$151.43	$151.45	$151.40
Purchase #2	$84.75	7.316%	$90.9503	$90.95	$90.95	$91.00
Purchase #3	$58.95	5.342%	$62.0991	$62.10	$62.10	$62.10
Purchase #4	$79.47	7.658%	$85.5558	$85.56	$85.55	$85.60
Purchase #5	$43.44	11.788%	$48.5607	$48.56	$48.55	$48.60
Purchase #6	$150.76	11.341%	$167.8577	$167.86	$167.85	$167.90
Purchase #7	$78.87	3.452%	$81.5926	$81.59	$81.60	$81.60
7 purchase totals =	$639.99		$688.0425	$688.05	$688.05	$688.20