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	$236.76	9.623%	$259.5434	$259.54	$259.55	$259.50
Purchase #2	$89.43	6.865%	$95.5694	$95.57	$95.55	$95.60
Purchase #3	$84.87	6.225%	$90.1532	$90.15	$90.15	$90.20
Purchase #4	$81.28	13.167%	$91.9821	$91.98	$92.00	$92.00
Purchase #5	$199.48	6.117%	$211.6822	$211.68	$211.70	$211.70
Purchase #6	$102.58	3.665%	$106.3396	$106.34	$106.35	$106.30
Purchase #7	$215.83	4.656%	$225.879	$225.88	$225.90	$225.90
7 purchase totals =	$1,010.23		$1,081.1489	$1,081.14	$1,081.20	$1,081.20