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	$152.89	7.596%	$164.5035	$164.50	$164.50	$164.50
Purchase #2	$226.97	12.529%	$255.4071	$255.41	$255.40	$255.40
Purchase #3	$186.46	12.579%	$209.9148	$209.91	$209.90	$209.90
Purchase #4	$119.37	9.229%	$130.3867	$130.39	$130.40	$130.40
Purchase #5	$61.83	12.201%	$69.3739	$69.37	$69.35	$69.40
Purchase #6	$104.95	13.314%	$118.923	$118.92	$118.90	$118.90
Purchase #7	$198.41	8.670%	$215.6121	$215.61	$215.60	$215.60
7 purchase totals =	$1,050.88		$1,164.1211	$1,164.11	$1,164.05	$1,164.10