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	$128.76	4.697%	$134.8079	$134.81	$134.80	$134.80
Purchase #2	$97.54	4.348%	$101.781	$101.78	$101.80	$101.80
Purchase #3	$62.87	3.419%	$65.0195	$65.02	$65.00	$65.00
Purchase #4	$94.35	9.811%	$103.6067	$103.61	$103.60	$103.60
Purchase #5	$31.91	5.299%	$33.6009	$33.60	$33.60	$33.60
Purchase #6	$201.42	8.619%	$218.7804	$218.78	$218.80	$218.80
Purchase #7	$79.94	3.749%	$82.937	$82.94	$82.95	$82.90
7 purchase totals =	$696.79		$740.5334	$740.54	$740.55	$740.50