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	$219.51	10.670%	$242.9317	$242.93	$242.95	$242.90
Purchase #2	$120.93	11.519%	$134.8599	$134.86	$134.85	$134.90
Purchase #3	$13.98	4.164%	$14.5621	$14.56	$14.55	$14.60
Purchase #4	$190.42	4.340%	$198.6842	$198.68	$198.70	$198.70
Purchase #5	$98.42	13.162%	$111.374	$111.37	$111.35	$111.40
Purchase #6	$64.83	7.263%	$69.5386	$69.54	$69.55	$69.50
Purchase #7	$120.56	9.204%	$131.6563	$131.66	$131.65	$131.70
7 purchase totals =	$828.65		$903.6068	$903.60	$903.60	$903.70