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	$31.41	13.321%	$35.5941	$35.59	$35.60	$35.60
Purchase #2	$37.56	3.304%	$38.801	$38.80	$38.80	$38.80
Purchase #3	$118.61	13.671%	$134.8252	$134.83	$134.85	$134.80
Purchase #4	$182.42	5.546%	$192.537	$192.54	$192.55	$192.50
Purchase #5	$30.92	8.284%	$33.4814	$33.48	$33.50	$33.50
Purchase #6	$75.50	9.446%	$82.6317	$82.63	$82.65	$82.60
Purchase #7	$92.78	5.250%	$97.651	$97.65	$97.65	$97.70
7 purchase totals =	$569.20		$615.5214	$615.52	$615.60	$615.50