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	$115.42	3.151%	$119.0569	$119.06	$119.05	$119.10
Purchase #2	$173.44	8.617%	$188.3853	$188.39	$188.40	$188.40
Purchase #3	$114.40	7.774%	$123.2935	$123.29	$123.30	$123.30
Purchase #4	$142.89	10.475%	$157.8577	$157.86	$157.85	$157.90
Purchase #5	$23.33	6.828%	$24.923	$24.92	$24.90	$24.90
Purchase #6	$66.44	8.415%	$72.0309	$72.03	$72.05	$72.00
Purchase #7	$125.37	4.819%	$131.4116	$131.41	$131.40	$131.40
7 purchase totals =	$761.29		$816.9589	$816.96	$816.95	$817.00