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	$93.80	11.419%	$104.511	$104.51	$104.50	$104.50
Purchase #2	$23.63	7.703%	$25.4502	$25.45	$25.45	$25.50
Purchase #3	$101.89	9.132%	$111.1946	$111.19	$111.20	$111.20
Purchase #4	$69.80	5.326%	$73.5175	$73.52	$73.50	$73.50
Purchase #5	$196.41	6.631%	$209.4339	$209.43	$209.45	$209.40
Purchase #6	$155.74	8.283%	$168.6399	$168.64	$168.65	$168.60
Purchase #7	$179.54	6.510%	$191.2281	$191.23	$191.25	$191.20
7 purchase totals =	$820.81		$883.9752	$883.97	$884.00	$883.90