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	$58.80	5.337%	$61.9382	$61.94	$61.95	$61.90
Purchase #2	$140.25	5.366%	$147.7758	$147.78	$147.80	$147.80
Purchase #3	$210.73	3.570%	$218.2531	$218.25	$218.25	$218.30
Purchase #4	$50.28	7.845%	$54.2245	$54.22	$54.20	$54.20
Purchase #5	$85.69	5.165%	$90.1159	$90.12	$90.10	$90.10
Purchase #6	$160.91	6.726%	$171.7328	$171.73	$171.75	$171.70
Purchase #7	$126.54	13.403%	$143.5002	$143.50	$143.50	$143.50
7 purchase totals =	$833.20		$887.5405	$887.54	$887.55	$887.50