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	$126.47	3.761%	$131.2265	$131.23	$131.25	$131.20
Purchase #2	$7.63	11.716%	$8.5239	$8.52	$8.50	$8.50
Purchase #3	$158.54	3.642%	$164.314	$164.31	$164.30	$164.30
Purchase #4	$214.52	11.203%	$238.5527	$238.55	$238.55	$238.60
Purchase #5	$94.69	3.751%	$98.2418	$98.24	$98.25	$98.20
Purchase #6	$146.98	6.229%	$156.1354	$156.14	$156.15	$156.10
Purchase #7	$103.25	12.570%	$116.2285	$116.23	$116.25	$116.20
7 purchase totals =	$852.08		$913.2228	$913.22	$913.25	$913.10