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	$60.29	9.179%	$65.824	$65.82	$65.80	$65.80
Purchase #2	$152.40	7.872%	$164.3969	$164.40	$164.40	$164.40
Purchase #3	$133.42	5.649%	$140.9569	$140.96	$140.95	$141.00
Purchase #4	$135.39	6.578%	$144.296	$144.30	$144.30	$144.30
Purchase #5	$25.92	4.693%	$27.1364	$27.14	$27.15	$27.10
Purchase #6	$223.53	3.296%	$230.8975	$230.90	$230.90	$230.90
Purchase #7	$30.60	9.164%	$33.4042	$33.40	$33.40	$33.40
7 purchase totals =	$761.55		$806.9119	$806.92	$806.90	$806.90