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	$169.82	3.308%	$175.4376	$175.44	$175.45	$175.40
Purchase #2	$80.53	5.476%	$84.9398	$84.94	$84.95	$84.90
Purchase #3	$84.27	5.406%	$88.8256	$88.83	$88.85	$88.80
Purchase #4	$159.31	8.151%	$172.2954	$172.30	$172.30	$172.30
Purchase #5	$92.68	7.416%	$99.5531	$99.55	$99.55	$99.60
Purchase #6	$88.80	12.538%	$99.9337	$99.93	$99.95	$99.90
Purchase #7	$31.28	7.402%	$33.5953	$33.60	$33.60	$33.60
7 purchase totals =	$706.69		$754.5805	$754.59	$754.65	$754.50