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	$54.65	4.408%	$57.059	$57.06	$57.05	$57.10
Purchase #2	$49.80	13.711%	$56.6281	$56.63	$56.65	$56.60
Purchase #3	$176.59	10.165%	$194.5404	$194.54	$194.55	$194.50
Purchase #4	$105.85	3.725%	$109.7929	$109.79	$109.80	$109.80
Purchase #5	$130.74	9.313%	$142.9158	$142.92	$142.90	$142.90
Purchase #6	$17.51	9.212%	$19.123	$19.12	$19.10	$19.10
Purchase #7	$206.86	4.455%	$216.0756	$216.08	$216.10	$216.10
7 purchase totals =	$742.00		$796.1348	$796.14	$796.15	$796.10