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	$158.89	5.294%	$167.3016	$167.30	$167.30	$167.30
Purchase #2	$198.71	6.847%	$212.3157	$212.32	$212.30	$212.30
Purchase #3	$160.51	10.104%	$176.7279	$176.73	$176.75	$176.70
Purchase #4	$172.71	5.713%	$182.5769	$182.58	$182.60	$182.60
Purchase #5	$21.28	5.820%	$22.5185	$22.52	$22.50	$22.50
Purchase #6	$42.38	5.732%	$44.8092	$44.81	$44.80	$44.80
Purchase #7	$142.54	5.426%	$150.2742	$150.27	$150.25	$150.30
7 purchase totals =	$897.02		$956.5240	$956.53	$956.50	$956.50