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	$35.74	8.626%	$38.8229	$38.82	$38.80	$38.80
Purchase #2	$212.56	4.153%	$221.3876	$221.39	$221.40	$221.40
Purchase #3	$53.86	4.202%	$56.1232	$56.12	$56.10	$56.10
Purchase #4	$164.81	10.333%	$181.8398	$181.84	$181.85	$181.80
Purchase #5	$152.70	3.449%	$157.9666	$157.97	$157.95	$158.00
Purchase #6	$56.94	5.144%	$59.869	$59.87	$59.85	$59.90
Purchase #7	$78.39	10.791%	$86.8491	$86.85	$86.85	$86.80
7 purchase totals =	$755.00		$802.8582	$802.86	$802.80	$802.80