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	$119.27	7.758%	$128.523	$128.52	$128.50	$128.50
Purchase #2	$112.73	3.854%	$117.0746	$117.07	$117.05	$117.10
Purchase #3	$39.82	9.395%	$43.5611	$43.56	$43.55	$43.60
Purchase #4	$36.98	10.371%	$40.8152	$40.82	$40.80	$40.80
Purchase #5	$168.46	11.653%	$188.0906	$188.09	$188.10	$188.10
Purchase #6	$105.25	11.372%	$117.219	$117.22	$117.20	$117.20
Purchase #7	$116.28	6.401%	$123.7231	$123.72	$123.70	$123.70
7 purchase totals =	$698.79		$759.0066	$759.00	$758.90	$759.00