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	$219.80	6.158%	$233.3353	$233.34	$233.35	$233.30
Purchase #2	$50.47	12.791%	$56.9256	$56.93	$56.95	$56.90
Purchase #3	$13.83	9.606%	$15.1585	$15.16	$15.15	$15.20
Purchase #4	$102.32	10.594%	$113.1598	$113.16	$113.15	$113.20
Purchase #5	$220.38	11.559%	$245.8537	$245.85	$245.85	$245.90
Purchase #6	$238.39	10.473%	$263.3566	$263.36	$263.35	$263.40
Purchase #7	$115.64	7.308%	$124.091	$124.09	$124.10	$124.10
7 purchase totals =	$960.83		$1,051.8805	$1,051.89	$1,051.90	$1,052.00