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	$58.98	11.522%	$65.7757	$65.78	$65.80	$65.80
Purchase #2	$65.57	11.742%	$73.2692	$73.27	$73.25	$73.30
Purchase #3	$225.53	11.652%	$251.8088	$251.81	$251.80	$251.80
Purchase #4	$31.78	6.225%	$33.7583	$33.76	$33.75	$33.80
Purchase #5	$64.76	12.306%	$72.7294	$72.73	$72.75	$72.70
Purchase #6	$97.40	12.690%	$109.7601	$109.76	$109.75	$109.80
Purchase #7	$247.83	13.806%	$282.0454	$282.05	$282.05	$282.00
7 purchase totals =	$791.85		$889.1469	$889.16	$889.15	$889.20