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	$213.89	9.320%	$233.8245	$233.82	$233.80	$233.80
Purchase #2	$231.33	7.678%	$249.0915	$249.09	$249.10	$249.10
Purchase #3	$30.63	10.584%	$33.8719	$33.87	$33.85	$33.90
Purchase #4	$139.57	4.616%	$146.0126	$146.01	$146.00	$146.00
Purchase #5	$98.85	10.705%	$109.4319	$109.43	$109.45	$109.40
Purchase #6	$6.60	12.466%	$7.4228	$7.42	$7.40	$7.40
Purchase #7	$205.32	7.591%	$220.9058	$220.91	$220.90	$220.90
7 purchase totals =	$926.19		$1,000.5610	$1,000.55	$1,000.50	$1,000.50