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	$239.74	13.808%	$272.8433	$272.84	$272.85	$272.80
Purchase #2	$38.27	3.833%	$39.7369	$39.74	$39.75	$39.70
Purchase #3	$84.72	7.183%	$90.8054	$90.81	$90.80	$90.80
Purchase #4	$95.89	9.741%	$105.2306	$105.23	$105.25	$105.20
Purchase #5	$180.49	4.166%	$188.0092	$188.01	$188.00	$188.00
Purchase #6	$136.30	5.190%	$143.374	$143.37	$143.35	$143.40
Purchase #7	$165.53	3.479%	$171.2888	$171.29	$171.30	$171.30
7 purchase totals =	$940.94		$1,011.2882	$1,011.29	$1,011.30	$1,011.20