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	$142.77	13.475%	$162.0083	$162.01	$162.00	$162.00
Purchase #2	$131.81	3.426%	$136.3258	$136.33	$136.35	$136.30
Purchase #3	$102.79	9.506%	$112.5612	$112.56	$112.55	$112.60
Purchase #4	$120.72	7.458%	$129.7233	$129.72	$129.70	$129.70
Purchase #5	$10.29	4.422%	$10.745	$10.75	$10.75	$10.70
Purchase #6	$119.33	3.292%	$123.2583	$123.26	$123.25	$123.30
Purchase #7	$243.77	5.308%	$256.7093	$256.71	$256.70	$256.70
7 purchase totals =	$871.48		$931.3312	$931.34	$931.30	$931.30