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	$26.58	6.443%	$28.2925	$28.29	$28.30	$28.30
Purchase #2	$104.69	6.345%	$111.3326	$111.33	$111.35	$111.30
Purchase #3	$84.29	7.501%	$90.6126	$90.61	$90.60	$90.60
Purchase #4	$151.40	10.688%	$167.5816	$167.58	$167.60	$167.60
Purchase #5	$191.96	3.441%	$198.5653	$198.57	$198.55	$198.60
Purchase #6	$24.50	12.400%	$27.538	$27.54	$27.55	$27.50
Purchase #7	$222.40	8.406%	$241.0949	$241.09	$241.10	$241.10
7 purchase totals =	$805.82		$865.0175	$865.01	$865.05	$865.00