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	$164.26	9.842%	$180.4265	$180.43	$180.45	$180.40
Purchase #2	$40.45	7.320%	$43.4109	$43.41	$43.40	$43.40
Purchase #3	$85.89	12.723%	$96.8178	$96.82	$96.80	$96.80
Purchase #4	$135.92	9.563%	$148.918	$148.92	$148.90	$148.90
Purchase #5	$215.58	10.378%	$237.9529	$237.95	$237.95	$238.00
Purchase #6	$249.35	12.800%	$281.2668	$281.27	$281.25	$281.30
Purchase #7	$54.40	4.828%	$57.0264	$57.03	$57.05	$57.00
7 purchase totals =	$945.85		$1,045.8193	$1,045.83	$1,045.80	$1,045.80