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	$73.86	9.461%	$80.8479	$80.85	$80.85	$80.80
Purchase #2	$6.95	5.599%	$7.3391	$7.34	$7.35	$7.30
Purchase #3	$233.38	13.581%	$265.0753	$265.08	$265.10	$265.10
Purchase #4	$36.63	10.538%	$40.4901	$40.49	$40.50	$40.50
Purchase #5	$158.52	13.867%	$180.502	$180.50	$180.50	$180.50
Purchase #6	$234.46	12.857%	$264.6045	$264.60	$264.60	$264.60
Purchase #7	$163.63	7.280%	$175.5423	$175.54	$175.55	$175.50
7 purchase totals =	$907.43		$1,014.4012	$1,014.40	$1,014.45	$1,014.30