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	$139.51	7.638%	$150.1658	$150.17	$150.15	$150.20
Purchase #2	$126.82	3.372%	$131.0964	$131.10	$131.10	$131.10
Purchase #3	$28.26	7.570%	$30.3993	$30.40	$30.40	$30.40
Purchase #4	$89.51	12.282%	$100.5036	$100.50	$100.50	$100.50
Purchase #5	$238.85	10.836%	$264.7318	$264.73	$264.75	$264.70
Purchase #6	$22.43	13.540%	$25.467	$25.47	$25.45	$25.50
Purchase #7	$67.25	5.466%	$70.9259	$70.93	$70.95	$70.90
7 purchase totals =	$712.63		$773.2898	$773.30	$773.30	$773.30