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	$235.37	6.204%	$249.9724	$249.97	$249.95	$250.00
Purchase #2	$66.90	8.803%	$72.7892	$72.79	$72.80	$72.80
Purchase #3	$35.86	9.643%	$39.318	$39.32	$39.30	$39.30
Purchase #4	$142.48	6.870%	$152.2684	$152.27	$152.25	$152.30
Purchase #5	$148.49	9.458%	$162.5342	$162.53	$162.55	$162.50
Purchase #6	$188.67	13.470%	$214.0838	$214.08	$214.10	$214.10
Purchase #7	$204.73	7.803%	$220.7051	$220.71	$220.70	$220.70
7 purchase totals =	$1,022.50		$1,111.6711	$1,111.67	$1,111.65	$1,111.70