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	$211.72	12.850%	$238.926	$238.93	$238.95	$238.90
Purchase #2	$86.74	8.158%	$93.8162	$93.82	$93.80	$93.80
Purchase #3	$107.39	5.691%	$113.5016	$113.50	$113.50	$113.50
Purchase #4	$203.66	3.792%	$211.3828	$211.38	$211.40	$211.40
Purchase #5	$162.66	3.368%	$168.1384	$168.14	$168.15	$168.10
Purchase #6	$190.50	13.260%	$215.7603	$215.76	$215.75	$215.80
Purchase #7	$49.43	3.275%	$51.0488	$51.05	$51.05	$51.00
7 purchase totals =	$1,012.10		$1,092.5741	$1,092.58	$1,092.60	$1,092.50