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	$226.45	13.659%	$257.3808	$257.38	$257.40	$257.40
Purchase #2	$86.60	6.502%	$92.2307	$92.23	$92.25	$92.20
Purchase #3	$24.26	13.180%	$27.4575	$27.46	$27.45	$27.50
Purchase #4	$229.55	11.866%	$256.7884	$256.79	$256.80	$256.80
Purchase #5	$96.53	4.538%	$100.9105	$100.91	$100.90	$100.90
Purchase #6	$208.92	7.770%	$225.1531	$225.15	$225.15	$225.20
Purchase #7	$129.97	3.360%	$134.337	$134.34	$134.35	$134.30
7 purchase totals =	$1,002.28		$1,094.2580	$1,094.26	$1,094.30	$1,094.30