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	$196.90	5.546%	$207.8201	$207.82	$207.80	$207.80
Purchase #2	$32.34	9.585%	$35.4398	$35.44	$35.45	$35.40
Purchase #3	$18.50	9.658%	$20.2867	$20.29	$20.30	$20.30
Purchase #4	$240.72	8.561%	$261.328	$261.33	$261.35	$261.30
Purchase #5	$97.33	8.814%	$105.9087	$105.91	$105.90	$105.90
Purchase #6	$115.81	7.380%	$124.3568	$124.36	$124.35	$124.40
Purchase #7	$238.94	3.149%	$246.4642	$246.46	$246.45	$246.50
7 purchase totals =	$940.54		$1,001.6043	$1,001.61	$1,001.60	$1,001.60