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	$139.67	10.691%	$154.6021	$154.60	$154.60	$154.60
Purchase #2	$42.74	11.713%	$47.7461	$47.75	$47.75	$47.70
Purchase #3	$65.34	3.627%	$67.7099	$67.71	$67.70	$67.70
Purchase #4	$221.95	8.139%	$240.0145	$240.01	$240.00	$240.00
Purchase #5	$152.88	10.304%	$168.6328	$168.63	$168.65	$168.60
Purchase #6	$205.84	13.618%	$233.8713	$233.87	$233.85	$233.90
Purchase #7	$150.69	11.870%	$168.5769	$168.58	$168.60	$168.60
7 purchase totals =	$979.11		$1,081.1536	$1,081.15	$1,081.15	$1,081.10