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	10.228%	$68.9256	$68.93	$68.95	$68.90
Purchase #2	$198.44	13.469%	$225.1679	$225.17	$225.15	$225.20
Purchase #3	$65.80	10.146%	$72.4761	$72.48	$72.50	$72.50
Purchase #4	$40.31	12.462%	$45.3334	$45.33	$45.35	$45.30
Purchase #5	$97.48	5.713%	$103.049	$103.05	$103.05	$103.00
Purchase #6	$85.75	12.491%	$96.461	$96.46	$96.45	$96.50
Purchase #7	$137.61	3.402%	$142.2915	$142.29	$142.30	$142.30
7 purchase totals =	$687.92		$753.7045	$753.71	$753.75	$753.70