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	$109.66	7.834%	$118.2508	$118.25	$118.25	$118.30
Purchase #2	$237.28	11.584%	$264.7665	$264.77	$264.75	$264.80
Purchase #3	$34.54	9.377%	$37.7788	$37.78	$37.80	$37.80
Purchase #4	$250.39	10.470%	$276.6058	$276.61	$276.60	$276.60
Purchase #5	$78.43	5.374%	$82.6448	$82.64	$82.65	$82.60
Purchase #6	$167.77	5.167%	$176.4387	$176.44	$176.45	$176.40
Purchase #7	$109.97	8.508%	$119.3262	$119.33	$119.35	$119.30
7 purchase totals =	$988.04		$1,075.8116	$1,075.82	$1,075.85	$1,075.80