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	$178.40	8.156%	$192.9503	$192.95	$192.95	$193.00
Purchase #2	$246.32	7.746%	$265.3999	$265.40	$265.40	$265.40
Purchase #3	$156.34	4.203%	$162.911	$162.91	$162.90	$162.90
Purchase #4	$86.79	3.213%	$89.5786	$89.58	$89.60	$89.60
Purchase #5	$67.73	6.576%	$72.1839	$72.18	$72.20	$72.20
Purchase #6	$213.73	13.362%	$242.2886	$242.29	$242.30	$242.30
Purchase #7	$126.32	12.439%	$142.0329	$142.03	$142.05	$142.00
7 purchase totals =	$1,075.63		$1,167.3452	$1,167.34	$1,167.40	$1,167.40