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	$11.83	7.727%	$12.7441	$12.74	$12.75	$12.70
Purchase #2	$213.74	8.326%	$231.536	$231.54	$231.55	$231.50
Purchase #3	$174.83	12.277%	$196.2939	$196.29	$196.30	$196.30
Purchase #4	$170.98	4.515%	$178.6997	$178.70	$178.70	$178.70
Purchase #5	$215.85	8.813%	$234.8729	$234.87	$234.85	$234.90
Purchase #6	$24.26	5.482%	$25.5899	$25.59	$25.60	$25.60
Purchase #7	$151.40	11.503%	$168.8155	$168.82	$168.80	$168.80
7 purchase totals =	$962.89		$1,048.5520	$1,048.55	$1,048.55	$1,048.50