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	$8.48	4.796%	$8.8867	$8.89	$8.90	$8.90
Purchase #2	$64.85	10.330%	$71.549	$71.55	$71.55	$71.50
Purchase #3	$79.42	3.263%	$82.0115	$82.01	$82.00	$82.00
Purchase #4	$80.96	10.506%	$89.4657	$89.47	$89.45	$89.50
Purchase #5	$167.56	9.834%	$184.0379	$184.04	$184.05	$184.00
Purchase #6	$52.38	3.656%	$54.295	$54.30	$54.30	$54.30
Purchase #7	$162.88	8.157%	$176.1661	$176.17	$176.15	$176.20
7 purchase totals =	$616.53		$666.4119	$666.43	$666.40	$666.40