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	$24.80	5.329%	$26.1216	$26.12	$26.10	$26.10
Purchase #2	$72.48	6.404%	$77.1216	$77.12	$77.10	$77.10
Purchase #3	$140.32	10.616%	$155.2164	$155.22	$155.20	$155.20
Purchase #4	$68.91	3.662%	$71.4335	$71.43	$71.45	$71.40
Purchase #5	$94.31	6.277%	$100.2298	$100.23	$100.25	$100.20
Purchase #6	$131.60	12.753%	$148.3829	$148.38	$148.40	$148.40
Purchase #7	$131.42	3.696%	$136.2773	$136.28	$136.30	$136.30
7 purchase totals =	$663.84		$714.7831	$714.78	$714.80	$714.70