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	$71.60	6.858%	$76.5103	$76.51	$76.50	$76.50
Purchase #2	$86.81	4.356%	$90.5914	$90.59	$90.60	$90.60
Purchase #3	$33.75	4.155%	$35.1523	$35.15	$35.15	$35.20
Purchase #4	$220.62	5.618%	$233.0144	$233.01	$233.00	$233.00
Purchase #5	$89.99	9.847%	$98.8513	$98.85	$98.85	$98.90
Purchase #6	$61.45	6.232%	$65.2796	$65.28	$65.30	$65.30
Purchase #7	$185.55	7.170%	$198.8539	$198.85	$198.85	$198.90
7 purchase totals =	$749.77		$798.2532	$798.24	$798.25	$798.40