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	$130.86	13.541%	$148.5798	$148.58	$148.60	$148.60
Purchase #2	$142.99	9.262%	$156.2337	$156.23	$156.25	$156.20
Purchase #3	$105.48	7.485%	$113.3752	$113.38	$113.40	$113.40
Purchase #4	$38.77	12.648%	$43.6736	$43.67	$43.65	$43.70
Purchase #5	$166.44	7.792%	$179.409	$179.41	$179.40	$179.40
Purchase #6	$40.78	5.418%	$42.9895	$42.99	$43.00	$43.00
Purchase #7	$26.81	6.796%	$28.632	$28.63	$28.65	$28.60
7 purchase totals =	$652.13		$712.8928	$712.89	$712.95	$712.90