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	$134.28	8.379%	$145.5313	$145.53	$145.55	$145.50
Purchase #2	$164.34	8.502%	$178.3122	$178.31	$178.30	$178.30
Purchase #3	$81.94	9.278%	$89.5424	$89.54	$89.55	$89.50
Purchase #4	$65.74	12.445%	$73.9213	$73.92	$73.90	$73.90
Purchase #5	$202.29	8.562%	$219.6101	$219.61	$219.60	$219.60
Purchase #6	$33.39	3.260%	$34.4785	$34.48	$34.50	$34.50
Purchase #7	$194.90	12.631%	$219.5178	$219.52	$219.50	$219.50
7 purchase totals =	$876.88		$960.9136	$960.91	$960.90	$960.80