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	$162.91	7.672%	$175.4085	$175.41	$175.40	$175.40
Purchase #2	$57.68	8.438%	$62.547	$62.55	$62.55	$62.50
Purchase #3	$120.43	10.177%	$132.6862	$132.69	$132.70	$132.70
Purchase #4	$154.78	12.133%	$173.5595	$173.56	$173.55	$173.60
Purchase #5	$150.43	3.322%	$155.4273	$155.43	$155.45	$155.40
Purchase #6	$234.52	7.368%	$251.7994	$251.80	$251.80	$251.80
Purchase #7	$52.90	9.381%	$57.8625	$57.86	$57.85	$57.90
7 purchase totals =	$933.65		$1,009.2904	$1,009.30	$1,009.30	$1,009.30