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	$133.77	13.638%	$152.0136	$152.01	$152.00	$152.00
Purchase #2	$235.55	4.756%	$246.7528	$246.75	$246.75	$246.80
Purchase #3	$151.55	13.406%	$171.8668	$171.87	$171.85	$171.90
Purchase #4	$165.83	5.224%	$174.493	$174.49	$174.50	$174.50
Purchase #5	$119.27	7.596%	$128.3297	$128.33	$128.35	$128.30
Purchase #6	$10.56	7.807%	$11.3844	$11.38	$11.40	$11.40
Purchase #7	$38.30	6.836%	$40.9182	$40.92	$40.90	$40.90
7 purchase totals =	$854.83		$925.7585	$925.75	$925.75	$925.80