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	$154.28	11.659%	$172.2675	$172.27	$172.25	$172.30
Purchase #2	$158.39	13.717%	$180.1164	$180.12	$180.10	$180.10
Purchase #3	$76.47	13.220%	$86.5793	$86.58	$86.60	$86.60
Purchase #4	$244.67	13.839%	$278.5299	$278.53	$278.55	$278.50
Purchase #5	$54.48	4.635%	$57.0051	$57.01	$57.00	$57.00
Purchase #6	$124.95	12.375%	$140.4126	$140.41	$140.40	$140.40
Purchase #7	$145.91	12.452%	$164.0787	$164.08	$164.10	$164.10
7 purchase totals =	$959.15		$1,078.9895	$1,079.00	$1,079.00	$1,079.00