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	$141.93	5.714%	$150.0399	$150.04	$150.05	$150.00
Purchase #2	$136.90	3.622%	$141.8585	$141.86	$141.85	$141.90
Purchase #3	$175.36	6.691%	$187.0933	$187.09	$187.10	$187.10
Purchase #4	$62.79	11.507%	$70.0152	$70.02	$70.00	$70.00
Purchase #5	$173.53	10.478%	$191.7125	$191.71	$191.70	$191.70
Purchase #6	$125.49	4.716%	$131.4081	$131.41	$131.40	$131.40
Purchase #7	$91.82	6.465%	$97.7562	$97.76	$97.75	$97.80
7 purchase totals =	$907.82		$969.8837	$969.89	$969.85	$969.90