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	$5.71	3.870%	$5.931	$5.93	$5.95	$5.90
Purchase #2	$114.25	4.670%	$119.5855	$119.59	$119.60	$119.60
Purchase #3	$231.89	8.383%	$251.3293	$251.33	$251.35	$251.30
Purchase #4	$152.64	13.858%	$173.7929	$173.79	$173.80	$173.80
Purchase #5	$79.55	12.577%	$89.555	$89.56	$89.55	$89.60
Purchase #6	$54.26	4.224%	$56.5519	$56.55	$56.55	$56.60
Purchase #7	$48.67	12.160%	$54.5883	$54.59	$54.60	$54.60
7 purchase totals =	$686.97		$751.3339	$751.34	$751.40	$751.40