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	$62.53	11.781%	$69.8967	$69.90	$69.90	$69.90
Purchase #2	$76.57	6.245%	$81.3518	$81.35	$81.35	$81.40
Purchase #3	$95.71	5.670%	$101.1368	$101.14	$101.15	$101.10
Purchase #4	$18.86	13.177%	$21.3452	$21.35	$21.35	$21.30
Purchase #5	$36.54	10.300%	$40.3036	$40.30	$40.30	$40.30
Purchase #6	$133.49	7.859%	$143.981	$143.98	$144.00	$144.00
Purchase #7	$105.79	3.439%	$109.4281	$109.43	$109.45	$109.40
7 purchase totals =	$529.49		$567.4432	$567.45	$567.50	$567.40