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	$181.30	9.730%	$198.9405	$198.94	$198.95	$198.90
Purchase #2	$103.80	7.144%	$111.2155	$111.22	$111.20	$111.20
Purchase #3	$59.54	6.353%	$63.3226	$63.32	$63.30	$63.30
Purchase #4	$30.38	10.397%	$33.5386	$33.54	$33.55	$33.50
Purchase #5	$211.63	6.370%	$225.1108	$225.11	$225.10	$225.10
Purchase #6	$169.59	10.644%	$187.6412	$187.64	$187.65	$187.60
Purchase #7	$134.39	3.275%	$138.7913	$138.79	$138.80	$138.80
7 purchase totals =	$890.63		$958.5605	$958.56	$958.55	$958.40