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	$83.62	12.299%	$93.9044	$93.90	$93.90	$93.90
Purchase #2	$97.78	13.745%	$111.2199	$111.22	$111.20	$111.20
Purchase #3	$100.29	3.547%	$103.8473	$103.85	$103.85	$103.80
Purchase #4	$173.34	10.685%	$191.8614	$191.86	$191.85	$191.90
Purchase #5	$105.54	11.631%	$117.8154	$117.82	$117.80	$117.80
Purchase #6	$168.56	12.112%	$188.976	$188.98	$189.00	$189.00
Purchase #7	$179.52	4.553%	$187.6935	$187.69	$187.70	$187.70
7 purchase totals =	$908.65		$995.3179	$995.32	$995.30	$995.30