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	$194.40	6.870%	$207.7553	$207.76	$207.75	$207.80
Purchase #2	$38.50	9.422%	$42.1275	$42.13	$42.15	$42.10
Purchase #3	$217.71	6.324%	$231.478	$231.48	$231.50	$231.50
Purchase #4	$124.45	6.416%	$132.4347	$132.43	$132.45	$132.40
Purchase #5	$114.27	8.207%	$123.6481	$123.65	$123.65	$123.60
Purchase #6	$140.47	11.440%	$156.5398	$156.54	$156.55	$156.50
Purchase #7	$210.93	8.690%	$229.2598	$229.26	$229.25	$229.30
7 purchase totals =	$1,040.73		$1,123.2432	$1,123.25	$1,123.30	$1,123.20