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	$42.54	4.677%	$44.5296	$44.53	$44.55	$44.50
Purchase #2	$184.27	11.498%	$205.4574	$205.46	$205.45	$205.50
Purchase #3	$136.54	10.770%	$151.2454	$151.25	$151.25	$151.20
Purchase #4	$46.88	3.130%	$48.3473	$48.35	$48.35	$48.30
Purchase #5	$194.82	12.348%	$218.8764	$218.88	$218.90	$218.90
Purchase #6	$203.84	5.693%	$215.4446	$215.44	$215.45	$215.40
Purchase #7	$148.59	12.367%	$166.9661	$166.97	$166.95	$167.00
7 purchase totals =	$957.48		$1,050.8668	$1,050.88	$1,050.90	$1,050.80