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	$93.32	9.667%	$102.3412	$102.34	$102.35	$102.30
Purchase #2	$74.53	5.373%	$78.5345	$78.53	$78.55	$78.50
Purchase #3	$146.84	3.210%	$151.5536	$151.55	$151.55	$151.60
Purchase #4	$118.34	7.168%	$126.8226	$126.82	$126.80	$126.80
Purchase #5	$156.34	6.291%	$166.1753	$166.18	$166.20	$166.20
Purchase #6	$240.39	5.375%	$253.311	$253.31	$253.30	$253.30
Purchase #7	$115.26	13.854%	$131.2281	$131.23	$131.25	$131.20
7 purchase totals =	$945.02		$1,009.9663	$1,009.96	$1,010.00	$1,009.90