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	$118.29	12.575%	$133.165	$133.17	$133.15	$133.20
Purchase #2	$42.43	6.808%	$45.3186	$45.32	$45.30	$45.30
Purchase #3	$72.83	12.768%	$82.1289	$82.13	$82.15	$82.10
Purchase #4	$90.43	11.486%	$100.8168	$100.82	$100.80	$100.80
Purchase #5	$30.75	10.696%	$34.039	$34.04	$34.05	$34.00
Purchase #6	$182.34	6.421%	$194.0481	$194.05	$194.05	$194.00
Purchase #7	$22.77	11.159%	$25.3109	$25.31	$25.30	$25.30
7 purchase totals =	$559.84		$614.8273	$614.84	$614.80	$614.70