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	$166.95	4.554%	$174.5529	$174.55	$174.55	$174.60
Purchase #2	$162.57	6.372%	$172.929	$172.93	$172.95	$172.90
Purchase #3	$7.95	4.361%	$8.2967	$8.30	$8.30	$8.30
Purchase #4	$30.27	7.662%	$32.5893	$32.59	$32.60	$32.60
Purchase #5	$159.53	4.352%	$166.4727	$166.47	$166.45	$166.50
Purchase #6	$75.98	12.467%	$85.4524	$85.45	$85.45	$85.50
Purchase #7	$77.91	7.268%	$83.5725	$83.57	$83.55	$83.60
7 purchase totals =	$681.16		$723.8655	$723.86	$723.85	$724.00