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	$133.85	9.280%	$146.2713	$146.27	$146.25	$146.30
Purchase #2	$121.83	4.535%	$127.355	$127.36	$127.35	$127.40
Purchase #3	$18.40	3.314%	$19.0098	$19.01	$19.00	$19.00
Purchase #4	$128.66	7.124%	$137.8257	$137.83	$137.85	$137.80
Purchase #5	$83.40	10.869%	$92.4647	$92.46	$92.45	$92.50
Purchase #6	$176.68	4.712%	$185.0052	$185.01	$185.00	$185.00
Purchase #7	$200.29	8.564%	$217.4428	$217.44	$217.45	$217.40
7 purchase totals =	$863.11		$925.3745	$925.38	$925.35	$925.40