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	$192.98	11.585%	$215.3367	$215.34	$215.35	$215.30
Purchase #2	$40.46	5.416%	$42.6513	$42.65	$42.65	$42.70
Purchase #3	$61.67	4.421%	$64.3964	$64.40	$64.40	$64.40
Purchase #4	$207.26	5.450%	$218.5557	$218.56	$218.55	$218.60
Purchase #5	$49.64	6.706%	$52.9689	$52.97	$52.95	$53.00
Purchase #6	$79.55	13.706%	$90.4531	$90.45	$90.45	$90.50
Purchase #7	$148.91	12.527%	$167.564	$167.56	$167.55	$167.60
7 purchase totals =	$780.47		$851.9261	$851.93	$851.90	$852.10