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	$199.59	8.293%	$216.142	$216.14	$216.15	$216.10
Purchase #2	$53.93	10.544%	$59.6164	$59.62	$59.60	$59.60
Purchase #3	$152.51	9.599%	$167.1494	$167.15	$167.15	$167.10
Purchase #4	$216.70	6.388%	$230.5428	$230.54	$230.55	$230.50
Purchase #5	$18.98	4.310%	$19.798	$19.80	$19.80	$19.80
Purchase #6	$78.73	4.549%	$82.3114	$82.31	$82.30	$82.30
Purchase #7	$229.96	3.139%	$237.1784	$237.18	$237.20	$237.20
7 purchase totals =	$950.40		$1,012.7384	$1,012.74	$1,012.75	$1,012.60