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	$162.33	4.270%	$169.2615	$169.26	$169.25	$169.30
Purchase #2	$55.52	6.475%	$59.1149	$59.11	$59.10	$59.10
Purchase #3	$134.54	5.751%	$142.2774	$142.28	$142.30	$142.30
Purchase #4	$174.25	9.484%	$190.7759	$190.78	$190.80	$190.80
Purchase #5	$12.40	13.423%	$14.0645	$14.06	$14.05	$14.10
Purchase #6	$196.97	9.556%	$215.7925	$215.79	$215.80	$215.80
Purchase #7	$123.88	8.285%	$134.1435	$134.14	$134.15	$134.10
7 purchase totals =	$859.89		$925.4302	$925.42	$925.45	$925.50