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	$102.53	11.415%	$114.2338	$114.23	$114.25	$114.20
Purchase #2	$155.77	4.524%	$162.817	$162.82	$162.80	$162.80
Purchase #3	$60.78	8.818%	$66.1396	$66.14	$66.15	$66.10
Purchase #4	$80.80	3.332%	$83.4923	$83.49	$83.50	$83.50
Purchase #5	$138.54	4.536%	$144.8242	$144.82	$144.80	$144.80
Purchase #6	$60.73	8.525%	$65.9072	$65.91	$65.90	$65.90
Purchase #7	$131.75	10.349%	$145.3848	$145.38	$145.40	$145.40
7 purchase totals =	$730.90		$782.7989	$782.79	$782.80	$782.70