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	$89.25	3.705%	$92.5567	$92.56	$92.55	$92.60
Purchase #2	$137.82	10.546%	$152.3545	$152.35	$152.35	$152.40
Purchase #3	$144.26	5.213%	$151.7803	$151.78	$151.80	$151.80
Purchase #4	$94.41	3.765%	$97.9645	$97.96	$97.95	$98.00
Purchase #5	$33.41	11.853%	$37.3701	$37.37	$37.35	$37.40
Purchase #6	$72.61	3.116%	$74.8725	$74.87	$74.85	$74.90
Purchase #7	$10.68	10.498%	$11.8012	$11.80	$11.80	$11.80
7 purchase totals =	$582.44		$618.6998	$618.69	$618.65	$618.90