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	$134.98	5.823%	$142.8399	$142.84	$142.85	$142.80
Purchase #2	$61.46	4.361%	$64.1403	$64.14	$64.15	$64.10
Purchase #3	$158.73	5.499%	$167.4586	$167.46	$167.45	$167.50
Purchase #4	$237.40	10.702%	$262.8065	$262.81	$262.80	$262.80
Purchase #5	$94.29	3.671%	$97.7514	$97.75	$97.75	$97.80
Purchase #6	$87.43	3.342%	$90.3519	$90.35	$90.35	$90.40
Purchase #7	$37.46	13.581%	$42.5474	$42.55	$42.55	$42.50
7 purchase totals =	$811.75		$867.8960	$867.90	$867.90	$867.90