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	$141.59	3.424%	$146.438	$146.44	$146.45	$146.40
Purchase #2	$233.32	11.265%	$259.6035	$259.60	$259.60	$259.60
Purchase #3	$226.98	11.699%	$253.5344	$253.53	$253.55	$253.50
Purchase #4	$98.37	10.776%	$108.9704	$108.97	$108.95	$109.00
Purchase #5	$135.66	12.154%	$152.1481	$152.15	$152.15	$152.10
Purchase #6	$190.79	7.553%	$205.2004	$205.20	$205.20	$205.20
Purchase #7	$38.46	10.801%	$42.6141	$42.61	$42.60	$42.60
7 purchase totals =	$1,065.17		$1,168.5089	$1,168.50	$1,168.50	$1,168.40