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	$65.30	11.620%	$72.8879	$72.89	$72.90	$72.90
Purchase #2	$49.54	13.236%	$56.0971	$56.10	$56.10	$56.10
Purchase #3	$200.38	4.688%	$209.7738	$209.77	$209.75	$209.80
Purchase #4	$147.95	3.713%	$153.4434	$153.44	$153.45	$153.40
Purchase #5	$35.79	12.512%	$40.268	$40.27	$40.25	$40.30
Purchase #6	$40.93	6.119%	$43.4345	$43.43	$43.45	$43.40
Purchase #7	$33.47	9.454%	$36.6343	$36.63	$36.65	$36.60
7 purchase totals =	$573.36		$612.5390	$612.53	$612.55	$612.50