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	$187.83	11.285%	$209.0266	$209.03	$209.05	$209.00
Purchase #2	$148.64	12.140%	$166.6849	$166.68	$166.70	$166.70
Purchase #3	$73.32	13.204%	$83.0012	$83.00	$83.00	$83.00
Purchase #4	$158.40	12.435%	$178.097	$178.10	$178.10	$178.10
Purchase #5	$40.56	9.806%	$44.5373	$44.54	$44.55	$44.50
Purchase #6	$246.49	10.309%	$271.9007	$271.90	$271.90	$271.90
Purchase #7	$57.73	7.669%	$62.1573	$62.16	$62.15	$62.20
7 purchase totals =	$912.97		$1,015.4050	$1,015.41	$1,015.45	$1,015.40