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	$161.43	9.546%	$176.8401	$176.84	$176.85	$176.80
Purchase #2	$192.79	8.437%	$209.0557	$209.06	$209.05	$209.10
Purchase #3	$72.95	12.451%	$82.033	$82.03	$82.05	$82.00
Purchase #4	$67.65	5.864%	$71.617	$71.62	$71.60	$71.60
Purchase #5	$86.91	4.416%	$90.7479	$90.75	$90.75	$90.70
Purchase #6	$132.53	7.338%	$142.2551	$142.26	$142.25	$142.30
Purchase #7	$144.98	12.234%	$162.7169	$162.72	$162.70	$162.70
7 purchase totals =	$859.24		$935.2657	$935.28	$935.25	$935.20