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	$106.64	7.533%	$114.6732	$114.67	$114.65	$114.70
Purchase #2	$24.57	5.185%	$25.844	$25.84	$25.85	$25.80
Purchase #3	$87.89	13.426%	$99.6901	$99.69	$99.70	$99.70
Purchase #4	$137.75	9.118%	$150.31	$150.31	$150.30	$150.30
Purchase #5	$226.94	6.119%	$240.8265	$240.83	$240.85	$240.80
Purchase #6	$163.28	12.272%	$183.3177	$183.32	$183.30	$183.30
Purchase #7	$174.25	6.308%	$185.2417	$185.24	$185.25	$185.20
7 purchase totals =	$921.32		$999.9032	$999.90	$999.90	$999.80