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	$109.40	3.805%	$113.5627	$113.56	$113.55	$113.60
Purchase #2	$87.86	10.752%	$97.3067	$97.31	$97.30	$97.30
Purchase #3	$161.42	3.840%	$167.6185	$167.62	$167.60	$167.60
Purchase #4	$172.62	4.773%	$180.8592	$180.86	$180.85	$180.90
Purchase #5	$179.68	9.336%	$196.4549	$196.45	$196.45	$196.50
Purchase #6	$142.29	4.515%	$148.7144	$148.71	$148.70	$148.70
Purchase #7	$30.70	8.857%	$33.4191	$33.42	$33.40	$33.40
7 purchase totals =	$883.97		$937.9355	$937.93	$937.85	$938.00