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	$124.90	13.189%	$141.3731	$141.37	$141.35	$141.40
Purchase #2	$222.95	6.827%	$238.1708	$238.17	$238.15	$238.20
Purchase #3	$42.59	4.851%	$44.656	$44.66	$44.65	$44.70
Purchase #4	$67.88	4.392%	$70.8613	$70.86	$70.85	$70.90
Purchase #5	$202.33	11.581%	$225.7618	$225.76	$225.75	$225.80
Purchase #6	$96.49	3.605%	$99.9685	$99.97	$99.95	$100.00
Purchase #7	$137.30	3.846%	$142.5806	$142.58	$142.60	$142.60
7 purchase totals =	$894.44		$963.3721	$963.37	$963.30	$963.60