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	$200.25	4.576%	$209.4134	$209.41	$209.40	$209.40
Purchase #2	$226.82	9.822%	$249.0983	$249.10	$249.10	$249.10
Purchase #3	$84.94	5.257%	$89.4053	$89.41	$89.40	$89.40
Purchase #4	$49.40	6.293%	$52.5087	$52.51	$52.50	$52.50
Purchase #5	$156.65	11.571%	$174.776	$174.78	$174.80	$174.80
Purchase #6	$26.60	11.607%	$29.6875	$29.69	$29.70	$29.70
Purchase #7	$191.34	12.483%	$215.225	$215.23	$215.25	$215.20
7 purchase totals =	$936.00		$1,020.1142	$1,020.13	$1,020.15	$1,020.10