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	$231.58	9.308%	$253.1355	$253.14	$253.15	$253.10
Purchase #2	$29.88	6.421%	$31.7986	$31.80	$31.80	$31.80
Purchase #3	$178.87	9.623%	$196.0827	$196.08	$196.10	$196.10
Purchase #4	$164.40	4.731%	$172.1778	$172.18	$172.20	$172.20
Purchase #5	$222.54	7.547%	$239.3351	$239.34	$239.35	$239.30
Purchase #6	$19.69	9.633%	$21.5867	$21.59	$21.60	$21.60
Purchase #7	$90.31	3.367%	$93.3507	$93.35	$93.35	$93.40
7 purchase totals =	$937.27		$1,007.4671	$1,007.48	$1,007.55	$1,007.50