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	$144.65	4.848%	$151.6626	$151.66	$151.65	$151.70
Purchase #2	$47.46	7.671%	$51.1007	$51.10	$51.10	$51.10
Purchase #3	$169.64	9.166%	$185.1892	$185.19	$185.20	$185.20
Purchase #4	$54.74	8.826%	$59.5714	$59.57	$59.55	$59.60
Purchase #5	$213.49	7.102%	$228.6521	$228.65	$228.65	$228.70
Purchase #6	$113.80	3.320%	$117.5782	$117.58	$117.60	$117.60
Purchase #7	$238.51	7.588%	$256.6081	$256.61	$256.60	$256.60
7 purchase totals =	$982.29		$1,050.3623	$1,050.36	$1,050.35	$1,050.50