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	$187.61	11.223%	$208.6655	$208.67	$208.65	$208.70
Purchase #2	$59.65	13.138%	$67.4868	$67.49	$67.50	$67.50
Purchase #3	$85.25	4.782%	$89.3267	$89.33	$89.35	$89.30
Purchase #4	$38.93	9.811%	$42.7494	$42.75	$42.75	$42.70
Purchase #5	$232.43	5.326%	$244.8092	$244.81	$244.80	$244.80
Purchase #6	$204.55	13.294%	$231.7429	$231.74	$231.75	$231.70
Purchase #7	$37.40	3.171%	$38.586	$38.59	$38.60	$38.60
7 purchase totals =	$845.82		$923.3665	$923.38	$923.40	$923.30