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	$61.29	7.148%	$65.671	$65.67	$65.65	$65.70
Purchase #2	$27.78	13.112%	$31.4225	$31.42	$31.40	$31.40
Purchase #3	$148.70	3.710%	$154.2168	$154.22	$154.20	$154.20
Purchase #4	$149.59	12.519%	$168.3172	$168.32	$168.30	$168.30
Purchase #5	$245.38	11.732%	$274.168	$274.17	$274.15	$274.20
Purchase #6	$131.69	12.745%	$148.4739	$148.47	$148.45	$148.50
Purchase #7	$91.95	12.871%	$103.7849	$103.78	$103.80	$103.80
7 purchase totals =	$856.38		$946.0543	$946.05	$945.95	$946.10