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	$59.77	4.208%	$62.2851	$62.29	$62.30	$62.30
Purchase #2	$183.26	5.527%	$193.3888	$193.39	$193.40	$193.40
Purchase #3	$104.74	7.785%	$112.894	$112.89	$112.90	$112.90
Purchase #4	$51.39	3.737%	$53.3104	$53.31	$53.30	$53.30
Purchase #5	$192.35	10.661%	$212.8564	$212.86	$212.85	$212.90
Purchase #6	$55.78	6.784%	$59.5641	$59.56	$59.55	$59.60
Purchase #7	$15.29	11.270%	$17.0132	$17.01	$17.00	$17.00
7 purchase totals =	$662.58		$711.3120	$711.31	$711.30	$711.40