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	$69.56	8.523%	$75.4886	$75.49	$75.50	$75.50
Purchase #2	$169.96	5.640%	$179.5457	$179.55	$179.55	$179.50
Purchase #3	$132.57	10.480%	$146.4633	$146.46	$146.45	$146.50
Purchase #4	$213.77	7.839%	$230.5274	$230.53	$230.55	$230.50
Purchase #5	$132.98	7.401%	$142.8218	$142.82	$142.80	$142.80
Purchase #6	$211.50	3.126%	$218.1115	$218.11	$218.10	$218.10
Purchase #7	$145.25	5.195%	$152.7957	$152.80	$152.80	$152.80
7 purchase totals =	$1,075.59		$1,145.7540	$1,145.76	$1,145.75	$1,145.70