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	$40.82	8.613%	$44.3358	$44.34	$44.35	$44.30
Purchase #2	$211.49	6.342%	$224.9027	$224.90	$224.90	$224.90
Purchase #3	$166.97	11.568%	$186.2851	$186.29	$186.30	$186.30
Purchase #4	$137.28	4.762%	$143.8173	$143.82	$143.80	$143.80
Purchase #5	$164.54	12.506%	$185.1174	$185.12	$185.10	$185.10
Purchase #6	$159.54	7.619%	$171.6954	$171.70	$171.70	$171.70
Purchase #7	$88.63	12.665%	$99.855	$99.86	$99.85	$99.90
7 purchase totals =	$969.27		$1,056.0087	$1,056.03	$1,056.00	$1,056.00