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	$229.78	13.754%	$261.3839	$261.38	$261.40	$261.40
Purchase #2	$79.51	8.275%	$86.0895	$86.09	$86.10	$86.10
Purchase #3	$139.35	6.424%	$148.3018	$148.30	$148.30	$148.30
Purchase #4	$178.36	7.341%	$191.4534	$191.45	$191.45	$191.50
Purchase #5	$118.41	8.292%	$128.2286	$128.23	$128.25	$128.20
Purchase #6	$95.98	5.609%	$101.3635	$101.36	$101.35	$101.40
Purchase #7	$140.93	7.857%	$152.0029	$152.00	$152.00	$152.00
7 purchase totals =	$982.32		$1,068.8236	$1,068.81	$1,068.85	$1,068.90