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	$187.68	3.855%	$194.9151	$194.92	$194.90	$194.90
Purchase #2	$89.43	3.757%	$92.7899	$92.79	$92.80	$92.80
Purchase #3	$207.35	4.720%	$217.1369	$217.14	$217.15	$217.10
Purchase #4	$25.96	13.212%	$29.3898	$29.39	$29.40	$29.40
Purchase #5	$235.61	12.839%	$265.86	$265.86	$265.85	$265.90
Purchase #6	$177.86	10.715%	$196.9177	$196.92	$196.90	$196.90
Purchase #7	$41.33	4.799%	$43.3134	$43.31	$43.30	$43.30
7 purchase totals =	$965.22		$1,040.3228	$1,040.33	$1,040.30	$1,040.30