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	$126.53	11.482%	$141.0582	$141.06	$141.05	$141.10
Purchase #2	$199.98	13.137%	$226.2514	$226.25	$226.25	$226.30
Purchase #3	$72.83	8.354%	$78.9142	$78.91	$78.90	$78.90
Purchase #4	$133.74	12.204%	$150.0616	$150.06	$150.05	$150.10
Purchase #5	$49.66	4.551%	$51.92	$51.92	$51.90	$51.90
Purchase #6	$245.70	13.450%	$278.7467	$278.75	$278.75	$278.70
Purchase #7	$210.99	6.690%	$225.1052	$225.11	$225.10	$225.10
7 purchase totals =	$1,039.43		$1,152.0573	$1,152.06	$1,152.00	$1,152.10