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	$243.36	10.349%	$268.5453	$268.55	$268.55	$268.50
Purchase #2	$36.28	5.197%	$38.1655	$38.17	$38.15	$38.20
Purchase #3	$157.27	3.727%	$163.1315	$163.13	$163.15	$163.10
Purchase #4	$138.93	12.224%	$155.9128	$155.91	$155.90	$155.90
Purchase #5	$80.51	12.545%	$90.61	$90.61	$90.60	$90.60
Purchase #6	$215.61	3.304%	$222.7338	$222.73	$222.75	$222.70
Purchase #7	$115.35	8.289%	$124.9114	$124.91	$124.90	$124.90
7 purchase totals =	$987.31		$1,064.0103	$1,064.01	$1,064.00	$1,063.90