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	$55.57	7.858%	$59.9367	$59.94	$59.95	$59.90
Purchase #2	$245.45	4.351%	$256.1295	$256.13	$256.15	$256.10
Purchase #3	$157.30	9.322%	$171.9635	$171.96	$171.95	$172.00
Purchase #4	$246.28	4.113%	$256.4095	$256.41	$256.40	$256.40
Purchase #5	$179.36	5.213%	$188.71	$188.71	$188.70	$188.70
Purchase #6	$23.89	6.369%	$25.4116	$25.41	$25.40	$25.40
Purchase #7	$14.30	10.470%	$15.7972	$15.80	$15.80	$15.80
7 purchase totals =	$922.15		$974.3580	$974.36	$974.35	$974.30