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	$59.72	13.481%	$67.7709	$67.77	$67.75	$67.80
Purchase #2	$6.90	9.432%	$7.5508	$7.55	$7.55	$7.60
Purchase #3	$49.45	13.272%	$56.013	$56.01	$56.00	$56.00
Purchase #4	$172.87	9.461%	$189.2252	$189.23	$189.25	$189.20
Purchase #5	$75.86	3.462%	$78.4863	$78.49	$78.50	$78.50
Purchase #6	$77.54	6.425%	$82.5219	$82.52	$82.50	$82.50
Purchase #7	$59.75	10.176%	$65.8302	$65.83	$65.85	$65.80
7 purchase totals =	$502.09		$547.3983	$547.40	$547.40	$547.40