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	$164.25	7.207%	$176.0875	$176.09	$176.10	$176.10
Purchase #2	$221.75	3.687%	$229.9259	$229.93	$229.95	$229.90
Purchase #3	$147.96	10.541%	$163.5565	$163.56	$163.55	$163.60
Purchase #4	$71.61	9.127%	$78.1458	$78.15	$78.15	$78.10
Purchase #5	$33.90	3.812%	$35.1923	$35.19	$35.20	$35.20
Purchase #6	$38.69	13.552%	$43.9333	$43.93	$43.95	$43.90
Purchase #7	$63.79	13.654%	$72.4999	$72.50	$72.50	$72.50
7 purchase totals =	$741.95		$799.3412	$799.35	$799.40	$799.30