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	$178.33	12.680%	$200.9422	$200.94	$200.95	$200.90
Purchase #2	$206.46	12.798%	$232.8828	$232.88	$232.90	$232.90
Purchase #3	$93.72	9.836%	$102.9383	$102.94	$102.95	$102.90
Purchase #4	$39.99	13.863%	$45.5338	$45.53	$45.55	$45.50
Purchase #5	$203.67	3.180%	$210.1467	$210.15	$210.15	$210.10
Purchase #6	$149.68	12.615%	$168.5621	$168.56	$168.55	$168.60
Purchase #7	$78.47	12.211%	$88.052	$88.05	$88.05	$88.10
7 purchase totals =	$950.32		$1,049.0579	$1,049.05	$1,049.10	$1,049.00