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	$148.59	3.153%	$153.275	$153.28	$153.30	$153.30
Purchase #2	$59.83	12.771%	$67.4709	$67.47	$67.45	$67.50
Purchase #3	$213.27	12.496%	$239.9202	$239.92	$239.90	$239.90
Purchase #4	$44.65	7.230%	$47.8782	$47.88	$47.90	$47.90
Purchase #5	$104.61	4.796%	$109.6271	$109.63	$109.65	$109.60
Purchase #6	$101.67	11.271%	$113.1292	$113.13	$113.15	$113.10
Purchase #7	$152.56	12.737%	$171.9916	$171.99	$172.00	$172.00
7 purchase totals =	$825.18		$903.2922	$903.30	$903.35	$903.30