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	$63.33	13.729%	$72.0246	$72.02	$72.00	$72.00
Purchase #2	$99.67	6.807%	$106.4545	$106.45	$106.45	$106.50
Purchase #3	$52.45	3.103%	$54.0775	$54.08	$54.10	$54.10
Purchase #4	$217.45	9.800%	$238.7601	$238.76	$238.75	$238.80
Purchase #5	$113.99	3.414%	$117.8816	$117.88	$117.90	$117.90
Purchase #6	$109.35	3.857%	$113.5676	$113.57	$113.55	$113.60
Purchase #7	$137.92	10.209%	$152.0003	$152.00	$152.00	$152.00
7 purchase totals =	$794.16		$854.7662	$854.76	$854.75	$854.90