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	$220.51	9.539%	$241.5444	$241.54	$241.55	$241.50
Purchase #2	$75.87	10.123%	$83.5503	$83.55	$83.55	$83.60
Purchase #3	$53.27	5.447%	$56.1716	$56.17	$56.15	$56.20
Purchase #4	$232.64	13.585%	$264.2441	$264.24	$264.25	$264.20
Purchase #5	$205.97	4.832%	$215.9225	$215.92	$215.90	$215.90
Purchase #6	$216.32	6.728%	$230.874	$230.87	$230.85	$230.90
Purchase #7	$238.33	12.550%	$268.2404	$268.24	$268.25	$268.20
7 purchase totals =	$1,242.91		$1,360.5473	$1,360.53	$1,360.50	$1,360.50