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	$105.55	5.774%	$111.6445	$111.64	$111.65	$111.60
Purchase #2	$176.48	11.445%	$196.6781	$196.68	$196.70	$196.70
Purchase #3	$204.79	12.608%	$230.6099	$230.61	$230.60	$230.60
Purchase #4	$119.25	12.111%	$133.6924	$133.69	$133.70	$133.70
Purchase #5	$64.85	4.516%	$67.7786	$67.78	$67.80	$67.80
Purchase #6	$188.45	13.308%	$213.5289	$213.53	$213.55	$213.50
Purchase #7	$58.80	12.160%	$65.9501	$65.95	$65.95	$66.00
7 purchase totals =	$918.17		$1,019.8825	$1,019.88	$1,019.95	$1,019.90