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	$71.65	6.527%	$76.3266	$76.33	$76.35	$76.30
Purchase #2	$160.76	3.342%	$166.1326	$166.13	$166.15	$166.10
Purchase #3	$247.60	3.560%	$256.4146	$256.41	$256.40	$256.40
Purchase #4	$94.56	6.626%	$100.8255	$100.83	$100.85	$100.80
Purchase #5	$68.98	12.175%	$77.3783	$77.38	$77.40	$77.40
Purchase #6	$178.53	12.242%	$200.3856	$200.39	$200.40	$200.40
Purchase #7	$71.77	13.378%	$81.3714	$81.37	$81.35	$81.40
7 purchase totals =	$893.85		$958.8346	$958.84	$958.90	$958.80