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	$91.25	7.855%	$98.4177	$98.42	$98.40	$98.40
Purchase #2	$24.58	13.421%	$27.8789	$27.88	$27.90	$27.90
Purchase #3	$14.50	8.660%	$15.7557	$15.76	$15.75	$15.80
Purchase #4	$125.26	13.825%	$142.5772	$142.58	$142.60	$142.60
Purchase #5	$151.25	9.792%	$166.0604	$166.06	$166.05	$166.10
Purchase #6	$75.84	3.311%	$78.3511	$78.35	$78.35	$78.40
Purchase #7	$240.56	6.117%	$255.2751	$255.28	$255.30	$255.30
7 purchase totals =	$723.24		$784.3161	$784.33	$784.35	$784.50