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	$205.39	8.475%	$222.7968	$222.80	$222.80	$222.80
Purchase #2	$164.75	13.458%	$186.9221	$186.92	$186.90	$186.90
Purchase #3	$30.83	8.424%	$33.4271	$33.43	$33.45	$33.40
Purchase #4	$110.25	13.248%	$124.8559	$124.86	$124.85	$124.90
Purchase #5	$104.61	4.705%	$109.5319	$109.53	$109.55	$109.50
Purchase #6	$145.61	3.769%	$151.098	$151.10	$151.10	$151.10
Purchase #7	$187.56	12.450%	$210.9112	$210.91	$210.90	$210.90
7 purchase totals =	$949.00		$1,039.5430	$1,039.55	$1,039.55	$1,039.50