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	$138.89	6.784%	$148.3123	$148.31	$148.30	$148.30
Purchase #2	$225.80	10.567%	$249.6603	$249.66	$249.65	$249.70
Purchase #3	$80.61	6.517%	$85.8634	$85.86	$85.85	$85.90
Purchase #4	$12.99	7.532%	$13.9684	$13.97	$13.95	$14.00
Purchase #5	$175.97	11.544%	$196.284	$196.28	$196.30	$196.30
Purchase #6	$106.37	3.162%	$109.7334	$109.73	$109.75	$109.70
Purchase #7	$228.98	7.215%	$245.5009	$245.50	$245.50	$245.50
7 purchase totals =	$969.61		$1,049.3227	$1,049.31	$1,049.30	$1,049.40