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	$232.51	12.320%	$261.1552	$261.16	$261.15	$261.20
Purchase #2	$182.38	8.726%	$198.2945	$198.29	$198.30	$198.30
Purchase #3	$75.84	8.216%	$82.071	$82.07	$82.05	$82.10
Purchase #4	$52.68	7.124%	$56.4329	$56.43	$56.45	$56.40
Purchase #5	$218.87	8.849%	$238.2378	$238.24	$238.25	$238.20
Purchase #6	$101.83	3.195%	$105.0835	$105.08	$105.10	$105.10
Purchase #7	$59.97	4.749%	$62.818	$62.82	$62.80	$62.80
7 purchase totals =	$924.08		$1,004.0929	$1,004.09	$1,004.10	$1,004.10