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	$78.98	8.482%	$85.6791	$85.68	$85.70	$85.70
Purchase #2	$135.93	6.314%	$144.5126	$144.51	$144.50	$144.50
Purchase #3	$83.88	7.549%	$90.2121	$90.21	$90.20	$90.20
Purchase #4	$67.55	7.383%	$72.5372	$72.54	$72.55	$72.50
Purchase #5	$202.64	9.660%	$222.215	$222.22	$222.20	$222.20
Purchase #6	$32.84	9.440%	$35.9401	$35.94	$35.95	$35.90
Purchase #7	$187.36	12.430%	$210.6488	$210.65	$210.65	$210.60
7 purchase totals =	$789.18		$861.7449	$861.75	$861.75	$861.60