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	$127.36	3.540%	$131.8685	$131.87	$131.85	$131.90
Purchase #2	$118.88	5.579%	$125.5123	$125.51	$125.50	$125.50
Purchase #3	$164.90	11.454%	$183.7876	$183.79	$183.80	$183.80
Purchase #4	$20.87	3.743%	$21.6512	$21.65	$21.65	$21.70
Purchase #5	$130.50	5.480%	$137.6514	$137.65	$137.65	$137.70
Purchase #6	$214.34	5.866%	$226.9132	$226.91	$226.90	$226.90
Purchase #7	$85.56	4.304%	$89.2425	$89.24	$89.25	$89.20
7 purchase totals =	$862.41		$916.6267	$916.62	$916.60	$916.70