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	$137.58	10.830%	$152.4799	$152.48	$152.50	$152.50
Purchase #2	$44.54	13.837%	$50.703	$50.70	$50.70	$50.70
Purchase #3	$67.41	7.318%	$72.3431	$72.34	$72.35	$72.30
Purchase #4	$201.84	5.523%	$212.9876	$212.99	$213.00	$213.00
Purchase #5	$153.93	5.254%	$162.0175	$162.02	$162.00	$162.00
Purchase #6	$65.67	10.525%	$72.5818	$72.58	$72.60	$72.60
Purchase #7	$142.34	3.510%	$147.3361	$147.34	$147.35	$147.30
7 purchase totals =	$813.31		$870.4490	$870.45	$870.50	$870.40