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	$50.92	11.865%	$56.9617	$56.96	$56.95	$57.00
Purchase #2	$78.69	4.545%	$82.2665	$82.27	$82.25	$82.30
Purchase #3	$245.88	10.396%	$271.4417	$271.44	$271.45	$271.40
Purchase #4	$186.37	7.525%	$200.3943	$200.39	$200.40	$200.40
Purchase #5	$125.63	8.687%	$136.5435	$136.54	$136.55	$136.50
Purchase #6	$151.58	8.652%	$164.6947	$164.69	$164.70	$164.70
Purchase #7	$203.69	10.183%	$224.4318	$224.43	$224.45	$224.40
7 purchase totals =	$1,042.76		$1,136.7342	$1,136.72	$1,136.75	$1,136.70